SQL Injection: A Guide for WordPress Users

If you’re serious about your website’s security, then it’s time to learn about the dangers of SQL injections and how you can combat them.

In this guide, we’ll explain in detail what an SQL injection attack looks like, and the exact steps you need to take to avoid one. Let’s take a look. You’ll learn all about how these attacks work, why they’re so important to defend against, and real-world examples of these vulnerabilities. Let’s dive in!

What is SQL?

Structured Query Language (SQL) is a Relational Database Management System that enables users to store and retrieve many types of data on computer systems.

SQL is hugely popular and is used in many content management systems (CMS) like WordPress today. Shortly after the language became popular in the scientific research community, the issue of the now-infamous SQL injection arose.

What is an SQL Injection (SQLi)?

In a nutshell, an SQL injection (SQLi) is an attack that allows a hacker to take advantage of a vulnerable SQL query to run their own query. SQL injections occur when an attacker is able to run their own SQL on a server.

This can affect any system using SQL or its derivatives to manage data, including WordPress sites.

The main goals of SQLi attacks are:

• Unauthorized data retrieval
• Modification of database entries
• Denial of Service (DoS) by deleting or corrupting data

SQLi can be used to access sensitive information, alter user permissions, or disrupt site operations. Due to its potential impact, it’s crucial for developers to implement proper security measures to prevent such attacks.

Quick Tip: Back Up Your Website Regularly!

Many seasoned developers keep off-server copies of all the SQL they’ve written for their WordPress sites. In the form of .sql files, these can be used in conjunction with a WordPress backup plugin to ensure that even if an attacker can thwart your security, you can recover in very little time. A WordPress backup plugin like BackupBuddy backs up your entire WordPress database and any other files in your WordPress installation.

Types of SQL Injections

Now that we’ve explored some of the damage SQL-based attacks can cause, it’s time to explore the more technical side of injections. There are a few important subsets of injection types you should know.

1. Classic SQL Injection (SQLi)

The most common type of injection, the classic version is when the attacker knows the SQL code in advance. This also happens to be the type of injection most used on WordPress; since WordPress is open source, the general public has access to all of its components, including its SQL queries.

We’ll jump into actual examples a bit later on, but with this form of injection, attackers often manipulate queries to “cancel out” the first part of one. They can then insert a custom query that the server will run as though the original developer wrote it.

2. Blind SQL Injection (SQLi)

Unlike the classic version, blind SQL injections occur when the attacker doesn’t have access to SQL code and simply has to make an educated guess. Additionally, this type requires far more skill than traditional SQLi, since the results of a successful attack are not displayed to the attacker.

That being said, there are many programs available that assist malicious users in grabbing their results bit-by-bit automatically.

3. Compounded SLQ Injection (SQLi)

This form of attack is when a separate attack is combined with SQLi to get the desired result. The most sophisticated out of the three subgroups, the attacker must execute an exploit that allows them to execute SQLi that wouldn’t work on its own. The exploits that most commonly accompany SQLi in this genre of attack are authentication breaches, Distributed Denial of Service (DDoS) attacks, DNS hijacking, and cross-site scripting attacks.

Why are WordPress Websites Vulnerable to SQL Injections?

WordPress is incredibly popular, powering over 43% of all websites, making WordPress an attractive target for potential attackers. Let’s explore why WordPress sites might be vulnerable to SQL injections and what this means for website owners.

WordPress functions using a combination of PHP and MySQL databases. This powerful duo stores and manages various types of data, from blog posts and comments to user accounts and e-commerce information. However, this reliance on databases also opens up potential avenues for SQL injection attacks.

Common vulnerabilities in WordPress sites often stem from:

• Forms that don’t properly sanitize user input
• Outdated plugins or themes with known security flaws
• Incorrectly configured database permissions

To illustrate, let’s consider a few real-world scenarios:

1. Login forms: An attacker might try to inject malicious SQL code into username or password fields to bypass authentication.
2. Search functions: If not properly secured, search queries could be manipulated to extract sensitive data from the database.
3. Contact forms: These are frequent targets for SQL injection attempts, especially on sites that haven’t been updated recently.

It’s worth noting that the WordPress core is generally quite secure against basic SQL injection attacks. However, vulnerabilities can still arise from:

• Custom code that doesn’t follow security best practices
• Third-party plugins or themes that haven’t been thoroughly vetted
• Outdated WordPress installations that miss critical security patches

The good news is that website owners can take proactive steps to protect their sites. Regularly updating WordPress, plugins, and themes is crucial. Additionally, using reputable security plugins and ensuring proper input sanitization in any custom code can significantly reduce the risk of SQL injection attacks.

Important Warnings Regarding SQL Injections

SQL Injection Example

Now that we’ve gotten those disclaimers out of the way, let’s look at SQLi examples. In order to understand these, you’ll need to know a bit of SQL jargon. 

SQL uses commands like SELECT to grab data, DROP TABLE to completely destroy a table within a database, DELETE to remove rows from a table, and more. Additionally, the ‘*’ character means “all” in SQL.

The most basic query in SQL is: SELECT * FROM TABLE_NAME. This says to essentially print out all data from a table named “TABLE_NAME”. 

When you submit data into a login form, that’s run through a PHP script that matches your credentials with a table of users. In our example, we’ll assume that we’re very bad at cyber security and have a completely unencrypted, cleartext table with columns called USER and PASS.

Preparing the Query

In our very badly-secured database, our table with usernames and passwords is called BADLY_DONE_TABLE. The query to authenticate a user logging in is simply: SELECT * FROM BADLY_DONE_TABLE WHERE USER = ‘[username from form]’ AND PASS = ‘[password from form]’.

As you can see, we are saying to grab the “list” of users, which should only be one, if the username and password that are entered into the form match. SQL also allows the keyword OR to be used in conditional statements, like the AND you see in our query.

Now, it’s time to craft our exploit.

Exploiting Our Unprotected SQL Query

Our query is set up to return the user if our username and password match. Keeping in mind that a single quote will end a string, we can type “Blahblahblah” as our username and then ‘OR ‘1’=’1.

We’re taking advantage of the fact that our query is dynamically formed and input is not “sanitized” before it’s executed. Essentially, we’re saying that if the number ‘1’ equals the number ‘1’ (surprisingly, it does!), then dump everything from the table, regardless of whether the credentials we entered are correct.

In 1998, this would have worked. Now, it generally takes far more skill in both SQL and SQLi to craft working exploits for WordPress.

If you’re interested in seeing current and previous injection exploits for WordPress, you can check out a CVE database. This contains an index of security threats with the product name, versions affected, and a general description of how the exploit works. Pretty much all exploits you’ll find on lists like these are already patched, but they’re great to use as learning materials.

How to Check for SQL Injection Vulnerabilities

After reading this, you’re probably wondering how to ensure that your WordPress site doesn’t become the next victim of an SQLi attack. The good news is that you don’t need to be a security professional to protect yourself from SQLi attacks!

• Be very careful about any PHP files you write or get from other sites and install (specifically, WordPress plugins). All it takes is a weakly-made PHP script that doesn’t sanitize user input to ruin your WordPress site.
• Use well-known security monitoring plugin like Solid Security Pro to alert you in case someone is attempting to commit this attack against your site so you can block it beforehand.
• Most importantly, you should always keep your WordPress site updated to the latest version. Many site owners hold off on updating for one reason or another, and this is the reason for the vast majority of data breaches.
• Keep your WordPress plugins and themes updated. We can’t say it enough. Vulnerable themes and plugins are the #1 reason WordPress sites get hacked.

5 Steps to Prevent WordPress SQL Injections

1. Download and Install the Solid Security Pro Plugin

To get started securing and protecting your site, download and install the Solid Security Pro plugin.

2. Activate Version Management to Keep WordPress Core, Plugins and Themes Updated

Simply put: You’re putting yourself at risk for an attack if you are running outdated versions of WordPress, plugins and themes on your website. Version updates often include patches for security issues in the code, including SQL injections and remote code execution (RCE) vulnerabilities, so it’s important to always run the latest version of all software installed on your WordPress website.

Updates will appear in your WordPress dashboard as soon as they’re available. Make a practice of running a backup and then running all available updates every time you login to your WordPress site. While the task of running updates may seem inconvenient or tiresome, it’s an important WordPress security best practice.

It is hard to keep track of every disclosed WordPress vulnerability—we keep track and share them in our WordPress Vulnerability Roundups—and compare that list to the versions of plugins and themes you have installed on your website. However, this doesn’t stop WordPress hackers from targeting plugins and themes with known vulnerabilities. Having software with known vulnerabilities installed on your site gives hackers the blueprints they need to take over your website.

The Version Management feature in the Solid Security Pro plugin allows you to auto-update WordPress, plugins, and themes. Beyond that, Version Management also has options to harden your website when you are running outdated software and scan for old websites.

To get started using Version Management, enable the module on the main page of the security settings.

Now click the Configure Settings button to take a closer look at the settings, all designed to protect your site.

• WordPress Updates – Automatically install the latest WordPress release.
• Plugin Updates – Automatically install the latest plugin updates. Enabling this setting will disable the WordPress auto-update plugins feature to prevent conflicts.
• Theme Updates – Automatically install the latest theme updates. Enabling this setting will disable the WordPress auto-update theme feature to prevent conflicts.
• Strengthen Site When Running Outdated Software –  Automatically add extra protections to the site when an available update has not been installed for a month.
• Scan For Old WordPress Sites – Run a daily scan of the hosting account for old WordPress sites that could allow an attacker to compromise the server. A single outdated WordPress site with a vulnerability could allow attackers to compromise all the other sites on the same hosting account.
• Auto Update If Fixes Vulnerability – This option works in tandem with the Solid Security Pro Site Scan to check your website for known WordPress, plugin, and theme vulnerabilities and apply a patch when one is available.

3. Scan Your Site For Vulnerable Plugins and Themes

The Solid Security Pro Site Scanner is another way to secure and protect your WordPress website from the number one cause of all software hacks: outdated plugins and themes with known vulnerabilities.  The Site Scanner checks your site for known vulnerabilities and automatically apply a patch if one is available.

The 3 Types of WordPress Vulnerabilities Checked

1. WordPress Vulnerabilities
2. Plugin Vulnerabilities
3. Theme Vulnerabilities

To enable the Site Scan on new installs, navigate to the Solid Security Pro settings and click the Enable button on the Site Scan settings module.

To trigger a manual Site Scan, click the Scan Now button on the Site Scan Widget located on the right side-bar of the security settings.

The Site Scan results will display in the widget.

If the Site Scan detects a vulnerability, click the vulnerability link to view the details page.

On the Site Scan vulnerability page, you will see if there is a fix available for the vulnerability. If there is a patch available, you can click the Update Plugin button to apply the fix on your website.

There can be a delay between when a patch is available and the Solid Security Vulnerability Database getting updated to reflect the fix. In this case, you can mute the notification to not receive any more alerts related to the vulnerability.

4. Activate File Change Detection

The key to quickly spotting a security breach is monitoring file changes on your website. The File Change Detection feature in Solid Security Pro will scan your website’s files and alert you when changes occur on your website.

There are several legitimate reasons you would see new file change activity in your logs, but if the changes made were unexpected, you should take the time to ensure the changes were not malicious. For example, if you see a change made to a plugin on the same date and time you updated the plugin, there would be no reason to investigate

To start monitoring file changes, enable File Change Detection on the main page of the security settings.

Once File Change Detection is enabled, Solid Security Pro will start scanning all of your website’s files in chunks. Scanning your files in chunks will help to reduce the resources required to monitor file changes.

The initial file change scan will create an index of your website’s files and their file hashes. A file hash is a shortened, nonhuman readable version of the content of the file.

After the initial scan completes, Solid Security Pro will continue to scan your file in chunks. If a file hash changes on one of the subsequent scans, that means the contents of the file have changed.You can also run a manual file change by clicking the Scan Files Now button in the File Change Detection settings.

File changes happen all the time, and getting an email alert for every change would quickly become overwhelming. And before you know it, it becomes a boy who cried wolf situation, and you start ignoring the file change alerts altogether.

The good news is that Solid Security Pro intelligently identifies legitimate changes to reduce notifications and how you can mute notifications for files that are expected to update frequently. You can manage all your Solid Security notifications from the Notification Center within the Solid Security plugin. From your WordPress admin dashboard, visit Security > Settings and locate the Notification Center module.

5. Turn on Two-Factor Authentication for Users That Make Changes to the Website

Two-factor authentication is a process of verifying a person’s identity by requiring two separate methods of verification. Google shared on its blog that using two-factor authentication can stop 100% of automated bot attacks. Not bad odds!

The Solid Security plugin allows you to activate two-factor authentication for your WordPress site so users must enter a secondary code to log in.

The three two-factor authentication methods provided by Solid Security Pro include:

1. Mobile App – The mobile app method is the most secure method of two-factor authentication provided by Solid Security Pro. This method requires you to use a free two-factor mobile app like Authy or Google Authenticator.
2. Email – The email method of two-factor will send time-sensitive codes to your user’s email address.
3. Backup Codes – A set of one-time use codes that can be used to login in the event the primary two-factor method is lost.

To start using Two-Factor Authentication on your website, enable the feature on the main page of the Solid Security Pro settings.

We’ve already outlined the steps to set up two-factor authentication on WordPress. If you followed our recommendations and enabled the force requirements for privileged users, the next thing you will see is the place to enter the two-factor token.

SQL Injection Prevention Best Practices

Preventing SQL injection attacks is crucial for maintaining the security of your WordPress website. Here are some best practices to follow:

1. Coding practices

• Only grant the minimum necessary database permissions to your application.
• Use parameterized queries instead of concatenating user input directly into SQL statements.
• Utilize ORM libraries that handle SQL injection protection automatically.
• Implement proper error handling to avoid exposing database structure in error messages.

2. Use of prepared statements

Prepared statements are one of the most effective ways to prevent SQL injection:

• Prepared statements separate the SQL logic from the data, making it impossible for malicious input to alter the intent of a query.
• Example in PHP:

$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username AND password = :password');
$stmt->execute(['username' => $username, 'password' => $password]);

• Performance boost: Prepared statements can be reused, potentially improving query performance.

3. Input sanitization

While prepared statements are preferred, proper input sanitization is still important:

• Only allow known good input rather than trying to block bad input.
• Use built-in PHP functions like mysqli_real_escape_string() or WordPress functions like esc_sql().
• Ensure that user input matches the expected data type (e.g., integers for IDs).
• Implement maximum length restrictions on user input to prevent buffer overflow attacks.

4. Additional measures

• Implement a WAF to filter out malicious requests before they reach your application.
• Keep WordPress core, themes, and plugins up to date to patch known vulnerabilities.
• Use reputable WordPress security plugins that offer SQL injection Regularly review your custom code and third-party plugins for potential SQL injection vulnerabilities.

Remember, security is an ongoing process, so stay informed about the latest threats and prevention techniques.

Wrapping Up: To a Safer Web, Together

Don’t worry if you’re feeling a bit overwhelmed when you discover all of the potential security threats that are seeking out your WordPress site. The truth is that the threats are many, but the solutions can be simple.

We hope this guide helped you understand the risk of SQL injection attacks on your WordPress site. By implementing a few WordPress security best practices, along with the 5 steps above, you’ll have a better line of defense.