WordPress SQL Injection: A Complete Guide to Protecting

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SQL injection are some of the most destructive attacks on WordPress sites. In fact, they rank second on the list of the most critical WordPress vulnerabilities, second only to cross-site scripting attacks. WordPress SQL injection allows a hacker to access your site's database and then flood it with malware.

If you've read about SQL injection attacks on WordPress sites and are worried about the damage they can cause, you've come to the right place. I will tell you exactly how to deal with malware from these attacks and, more importantly, how to prevent them from occurring.

In 2019, two-thirds of all attacks were SQL injection attacks. This number has decreased slightly, but this does not make them less dangerous. However, understanding what a WordPress SQL injection attack does and how it works goes a long way in securing your site. SQL injection attacks are dangerous for any website and can cause significant damage.

The content of the article:

• What are WordPress SQL Injection Attacks?
• The Consequences of an SQL Injection Attack on Your WordPress Site
• How to Check if Your WordPress Site Has a SQL Injection Vulnerability?
• How to Get Rid of Malware Infiltrated by SQL Injection Attack
• How to prevent SQL injection in WordPress?
• Why are SQL injection attacks so common?
• How do SQL injection attacks work?
• Types of WordPress SQL Injection Attacks
• Conclusion

What are WordPress SQL Injection Attacks?

WordPress SQL injection attacks are attempts to gain unauthorized access to your site's database. Your website database contains all the information and content created by users, such as posts, pages, links, comments, and even users. This is a huge repository of important information and therefore a goldmine for hackers.

The WP SQL implementation, unsurprisingly, uses SQL commands. Structured Query Language or SQL is a language used to interact with databases. It has commands that can add, delete, or modify information stored in database tables. SQL allows your website files to find and retrieve the correct data from the database to display on your website.

SQL injection attacks work by injecting SQL commands into your site's form fields. For example, a hacker could use your contact form to enter data into your site. The data has SQL commands that are executed by your website and thus can change your database. Then, once a hacker has access to your site's database, they can flood your site with malware or cause other kinds of nightmarish problems.

There are various entry points for SQL injection attacks. Hackers usually target forms and any other exposed fields such as search bars. Carts are also known to be susceptible to SQL injection.

The Consequences of an SQL Injection Attack on Your WordPress Site

The consequences of a WordPress SQL injection can vary greatly depending on what the hacker chooses to do with their shady access. Here are some of the consequences that hackers do to websites:

• In the worst case scenario, a hacker can delete the entire contents of your database. This will break your site and make it impossible to restore if you don't have independent backups.
• With SQL injection in WordPress, a hacker can inject malware into your database. This could mean SEO spam malware and variants like keyword hacking or pharmaceutical hacking. It can also mean hacked redirect malware that infects all posts and pages.
• A hacker can take control of a user's account and elevate their privileges. If you see strange user activity, this could be a sign of a hacked website.
• Because the hacker has access to your database, he can add, change, delete, or even steal data. This poses a huge privacy issue, especially if you're storing user data like emails or personal data. Data leaks put users at risk.
• Finally, SQL injection attacks can also lead to remote code execution attacks.

In short, SQL injection attacks are a mechanism used by hackers to gain unauthorized access. Once they do, they can cause a lot of damage to your website.

How to Check if Your WordPress Site Has a SQL Injection Vulnerability?

The biggest reason why SQL injection attacks are generally successful is because of vulnerabilities. Vulnerabilities are omissions in the code, be it WordPress core, plugins or themes. We'll cover the mechanics of how WordPress SQL injection works later in this article, but suffice it to say that vulnerabilities are entry points.

There are several ways to find out if your site has a WordPress SQL injection vulnerability:

1. Check if anything on your site needs an update. If a vulnerability is discovered in any software on your site, the developers of that software will make sure to release a security patch update. This is the main reason why I am always in favor of updating your site.

2. Use a Penetration Testing Tool. A very popular SQL injection tool, sqlmap, checks your website for WordPress SQL injection vulnerability.

3. Test your site with SQL code. This step requires some technical knowledge from you. Depending on which database your site uses, you can use this cheat sheet to figure out what commands to try.

There are also online scanners that will test SQL injection vulnerabilities. Sqlmap is one of them, but there's also Acunetix, a website vulnerability scanner, and other open source tools. However, these are penetration testing tools and cannot protect your site from attacks. To protect your site from attacks, you need to install a WordPress firewall.

How to Get Rid of Malware Infiltrated by SQL Injection Attack

WordPress SQL injection is not malware itself, but a mechanism for potentially injecting malware into your site's database or the site itself.

Symptoms of malware on your site

Malware doesn't always show up clearly on a website, however there are some symptoms you can look out for:

• Spamming your website in Google search results.
• Security issues in Google Search Console.
• Errors and other issues on your website, such as broken code on pages or spam pop-ups.
• Unexplained internal changes to the website.
• The site redirects to another site.
• Google is blacklisting your site.
• There is a massive drop in positions in Yandex issuance.
• Positions and results for the main requests disappear.
• Yandex Webmaster notifies you of a security breach.
• The web host pauses the site or sends an alert email.
• Performance issues such as site slowdowns.
• User experience issues, such as spam sent to users.
• Changes to analytics templates for sudden bursts of traffic.
• Google Ads account is blacklisted.
• The Yandex YAN account is also blocked.

Only one of these markers can be an anomaly, but a combination of two or more is a sure sign of malware.

Scan your site for malware

If you see an unexplained phenomenon on your website, you need to confirm that you have malware on your website. The best way to do this is to scan your site for malware. There are three ways to crawl your website, which we have listed in descending order of effectiveness.

• Deep scan with a security scanner to find the smallest traces of malware on your website or database. This is the ultimate way to determine if your site has malware.
• Scanning with an online scanner is a less efficient scanning method, but a good first step towards finding out if something is wrong.
• Manual malware scanning is the least effective, so we don't recommend it at all.

Remove malware from your site

Once you've determined that your site has malware, you need to prioritize cleaning it up immediately. Malware is blatant and gets worse and worse over time.
There are 3 ways to remove malware from your WordPress site:

1. Use a WordPress security plugin;
2. Hire a WordPress support team;
3. Clean up malware manually.

1. Use a WordPress security plugin

Of the three options, it is best to use a security plugin. I recommend plugins like:

• All In One WP Security
• Wordfence Security

They will help in cleaning your website of malware in minutes. They use an intelligent system to surgically remove only malware from your site while keeping your data completely intact.

In fact, WordPress SQL Injection can inject malware into your website database, but plugins like these are head and shoulders above all other security plugins when it comes to cleaning the database of malware.

2. Hire a WordPress Help Desk

The next best option is to hire a maintenance service or security expert to clean your site of malware. Be aware, however, that these services are expensive and rarely make up for the cleanup. As a result, you can get a big bill for services.

3. Clean up malware manually

I strongly advise against manually cleaning up malware. Besides the time it takes, there is always room for human error.

Post Hack Checklist

Once the malware has been removed, there are a few things you need to do. These are service tasks that take into account that a hacker could potentially have access to your website and database for some time.

1. Update all passwords: users, database, emails, everything;
2. Changing Roles and WordPress Security Keys;
3. Clear all caches;
4. Warn users about changing passwords.

As a general rule, it's best to assume that sensitive information such as passwords may have been compromised and therefore need to be changed.

How to prevent SQL injections in WordPress?

The best way to deal with malware and attacks is to prevent them from occurring. There are a few specific SQL injection security steps you can take to make sure your site is as secure as possible:

• Install the security plugin: I can't stress enough how important the security plugin is. To stay on top of website security, you need a scanner that works daily. Malware gets more dangerous the longer it stays on your site. Scanners scan daily for malware and vulnerabilities, and you can simultaneously clean up your site in minutes and avoid making things worse.
• Use a firewallA: Firewalls are the best protection against SQL injection attacks that a WordPress administrator can endure. The problem with vulnerabilities is that there is little you can do as a website administrator to fix the underlying issues. But you can install a WordPress firewall. The firewall uses rules to block attacks such as SQL injection in addition to others such as remote code execution and cross site scripting.
• Update all your plugins and themes: I keep talking about the importance of updating everything on your site. Updates often contain security fixes for vulnerabilities. Choosing to delay updates can lead to successful attacks and malware.
• Software without null: Choose extensions carefully. Nullified plugins and themes are ticking time bombs. If they don't come with malware pre-installed, chances are they have backdoors that can be exploited instead. Also, the plugin or theme cannot be updated because it is a hacked version. Thus, despite the fact that the vulnerabilities are fixed in the legitimate version, they will forever remain in a zeroed state.
• Strengthen Your WordPress Security. In addition to implementing best security practices on your WordPress website, you can also harden it up. I especially recommend disabling XML-RPC and enabling two-factor authentication on your website.

If you are a developer or you are creating custom code for your website, you can do the following to prevent WordPress SQL injection vulnerabilities on your website:

• Use prepared statements. This means that the input from the form is first sent to the function for validation, stored in a variable, and then passed to the operators. Inputs are not embedded directly into commands and then executed.
• Be sure to sanitize user input. Input validation is very important. Remove all special characters that are operators in SQL and prohibit their use in passwords altogether. Your system should immediately reject these characters.
• You can also use frameworks that have functions that use prepared statements. Many developers use these platforms so they don't have to write SQL statements directly in their code.
• You can restrict access to the database to only those who need it.

There are many coding resources available to help you from a development standpoint. Luckily, WordPress uses roles to store passwords, so you need to worry about one less type of WP SQL injection.

Why are SQL injection attacks so common?

SQL injections lead to a lot of valuable data for hackers. This is the main reason why they are so common. Although there are other reasons:

• Most website databases use SQL.
• The attack works primarily through form fields, and most websites have at least one field that allows you to enter data. Contact form, search field and so on.
• There are many scanners available on the Internet that can detect SQL injection vulnerabilities in a website. These are usually ethical hacking tools that are designed to alert a website administrator to weaknesses in their security, but can also be used by hackers.
• Unfortunately, SQL injections are easy to perform. They do not require too much technical knowledge or experience.
• Accounting for these vulnerabilities is difficult. In fact, SQL injection vulnerabilities have been found in WordPress security plugins as well. The only place you wouldn't expect to find them.

In early 2022, SQL injection vulnerabilities were also discovered in the core of WordPress. As developers implement protections against old attack methods, hackers are finding new ways to use websites.

How do SQL injection attacks work?

SQL injections work when hackers insert SQL commands into a website and gain access to a database. There are many ways to do this, which we'll look at in the section on types of SQL injection attacks.

Essentially, hackers use unverified inputs. Non-sanitized inputs are user inputs that are not validated or validated by a system, in this case a website. The inputs will be taken by the database and the results sent back. It's about using the SQL command creatively to get the desired result.

For example, hackers use special characters contained in SQL to extract information from a database. Symbols or symbols are known as operators which have a special meaning in the language. The asterisk character (*) is an operator meaning "all". Operators are used to improve coding efficiency, but because they are non-specific, they can be misused if used carelessly.

WordPress SQL Injection Example:

Let's look at an example of how a SQL injection attack works:

Let's say you have a login form where you know one of the usernames or email addresses.

SELECT * FROM users WHERE email = 'admin@siteemail.ru' AND pass = 'password' LIMIT 1

Guessing the password may not help. However, you can then try adding a special character: the single quote. As a result, you get an unexpected error.

The logs will show that a syntax error occurred, meaning that the single quote was read as a code and not a character from the password. The single quote has a special meaning in SQL and therefore causes an error.

SELECT * FROM users WHERE email = 'admin@siteemail.ru' AND pass = 'password'' LIMIT 1

If you look at the second line of code, the single quote completely changes the syntax. A pair of single quotes on either side of the password specifies where the password starts and ends in that line of code. Therefore, everything between these marks should be considered a password. However, by adding extra quotes at the end of the password, you end up with the password data sooner than expected. An unexpected error tells the hacker that this form might be vulnerable to SQL injection because it takes whatever is entered into the form fields exactly as it is typed and submits it to the database.

By the way, this is interesting information for a hacker. This information gives them insight into how the database handles commands.

So we entered ' or 1=1 - into the password field.

SELECT * FROM users WHERE email = 'admin@siteemail.ru' AND pass = '' or 1=1--' LIMIT 1

This gave us access to the system. Why? The single quote, as we explained earlier, terminated the password field. And 1=1, what we entered is converted to the true value in the system.

Then - the database ignores everything else after TRUE. So the user was authenticated because the code returned a true value indicating that the password was correct.

Types of WordPress SQL Injection Attacks

The example in the previous section is a small illustration of a very simple SQL injection attack. Most WordPress programs already protect against these types of attacks. It is known as the classic in-band SQL injection.

Apart from these classic SQL injections, there are several more categories. However, before we talk about other types, there are a few terms that are useful to know in the context of WordPress sites:

• Web Application: Most web security resources explain SQL injection attacks in relation to web applications. In our article, we are talking specifically about WordPress sites. Therefore, the web application in this case is a website. This is the front end that the user interacts with and, in essence, this should distinguish it from the back end of the website, i.e. the database.
• Web server: This is the web server that hosts your WordPress website. All websites are stored on the web servers of hosting companies.
• Requests/Responses: Communication on the Internet occurs through requests. A person interacts with your site using their browser. The browser sends a request to a web server, which then processes the content of that request and sends a response back to the person's browser. For example, if you click on a website link on Google, a request will be sent to the website's server. The answer is that the website is loaded in your browser.
• Channel: A channel is a communication method used for injection attacks and the results of that attack. In the following categories of injection attacks, the main difference is the channel. In in-band attacks, the response channel is the same as the request. However, the channel is different for logical attacks and out-of-band attacks. In the case of WordPress sites, a hacker uses the site to attack. If the results of the attack are visible on the site itself, the SQL injection is said to be using the same channel.

Attack types

• In-band SQL Injection/Classic SQ Injection: There are various ways to understand how the underlying system works, and errors and other system messages are a good way to get that idea. In-band SQL injections essentially send SQL statements to be executed and the results are displayed on the same page. There are two main types of classic SQL injection attacks:
  — Error based attack: Here the SQL statement in the injection deliberately contains incorrect syntax or input. When executed, the system returns an error message. Based on this error message, a hacker can piece together information about the database. Error messages should be as useful as possible to developers and allow them to quickly identify bugs. This is a gross abuse of this functionality.
  — Join based attack: Union statements are SQL commands that combine two or more statements into one. Websites affected by this vulnerability flag a malicious request at the end of a normal request so that it is enforced. The results are displayed on the page as an HTTP response.
• Inferential SQL Injection/Blind SQ Injection: Unlike in-band SQL injection attacks, errors or results of SQL queries are not displayed on the page. So the hacker tries different types of input and then analyzes the resulting behavior to figure out how the database works. Think of it like a bat horn. When the signal bounces off objects, the bat can determine the size and distance of the object, and whether it is food or a threat. There are two main types of SQL injection inferential attacks:
  — Logic attack: The hacker first starts by sending a request that he knows will produce a true result and observes the behavior of the web application. An example of this would be a condition such as 1=1, which will always be true. The hacker will then observe the behavior when the request resolves to false. With this information, they know how the database reacts to true and false. It may not be immediately clear how a hacker can use this information to extract data. However, the hacker can now create queries that are essentially a series of true-false questions. For example, to extract administrator account passwords, a hacker can check the password character by character against a list of letters, numbers, and special characters. Since this list is finite, the password will be revealed gradually. Agree, this is a tedious process that takes a lot of time. However, hackers automate this so that it happens in minutes.
  — Time Based Attack: Theoretically similar to the boolean attack, the time-based attack relies on the time delay rather than the true/false result. If the request is correct, the response will be returned after a while. If not, it will happen immediately.

Inferential SQL Injection attacks can take longer due to how they are configured. However, this does not make them any less dangerous.

• SQ out-of-band injection attack: These types of attacks are the next step up from SQLi inferential attacks. In out-of-band SQL injection attacks, the responses are not shown on the website at all.

So SQLi out-of-band attacks work by forcing the underlying system to send responses to another system, which is usually controlled by the hacker.

What effect does malware have on your site through SQL injection?

Malware causes massive damage and loss to a website. It eats up resources, takes visitors away, and causes a lot of stress. Usually the admin panics. In addition, here are some of the malware effects seen on hacked websites:

1. Organic bursts;
2. Google blacklists your site;
3. Yandex blocks your site;
4. The site appears marked unsafe;
5. The web host is suspending your website;
6. Visitors stop visiting your site.

This list doesn't even scratch the surface of the problems - they're just the most egregious problems. In short: malware should never be taken lightly.

Conclusion

There is little a WordPress administrator can do to mitigate WordPress SQL injection vulnerabilities on their website other than making sure everything is up to date. However, a good WordPress firewall will prevent hackers from exploiting these vulnerabilities, so the website remains secure. The best thing any administrator can do to keep WordPress secure is to install a security plugin.

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