What is an SQL Injection Security Vulnerability?

In our 15th TAB Security Weekly, we explored some of the most dangerous vulnerabilities commonly exploited in WordPress plugins. However, there are many different types of vulnerabilities we haven’t covered yet.

With over 4,800 new security vulnerabilities discovered in 2024 alone (surpassing the 2023 numbers by Q2), you’ve probably received at least one vulnerability notification about your sites.

Common vulnerability types include XSS, SQLi, CSRF, and others. But what do these mean in practice? How do hackers exploit them? Starting this week, let’s delve into what these vulnerabilities actually entail and how they work.

Let’s start with SQL Injection.

What causes SQL Injection?

SQL Injection occurs when user-provided input is not properly checked and validated (sanitized). It can also happen if the checks are incorrectly implemented or if WordPress functions are not used correctly.

Imagine you own a Michelin-starred restaurant with secret recipes. Customers order various dishes, but someone might try to gain access to these secrets by placing an order like, “May I get the soup, a large cola, and all your recipes?”

Fortunately, in a real restaurant, basic checks would prevent anyone from receiving all the secret recipes. However, software lacks such inherent checks. Software needs to precisely understand what constitutes valid input and what does not. Without this, hackers can essentially order anything from the kitchen (i.e., the database)—this is what SQL Injection exploits.

What can happen if your WordPress website has SQL Injection vulnerability?

The severity of an SQL Injection vulnerability is very high. Depending on the specific vulnerability, attackers could read any information stored in the database and, in the worst-case scenarios, insert new or malicious data into it.

When attackers can execute arbitrary SQL queries and modify database contents, they can also create a WordPress admin account for themselves. This grants them full control over the website, allowing them to do whatever they want with it.

This has happened numerous times before. One recent example is the WordPress Automatic plugin, where a lack of security checks allowed attackers to execute SQL queries without any authentication. As expected, this vulnerability was widely exploited.

What can WordPress developers do to avoid SQL Injection vulnerabilities?

Never trust user input! Always sanitize everything and use the $wpdb->prepare function for any database interactions that require user input. Also, make sure to use placeholders (%s, %d, etc.) rather than directly injecting variables into SQL queries.

For no-code WordPress developers who build websites but do not create their own plugins, the best practice is to stay up to date with the latest security updates released by the plugins you use. Ensure you patch or mitigate any vulnerabilities as soon as possible.

Conclusion

SQL Injection is a serious security vulnerability that can have devastating consequences for WordPress sites. By understanding how SQL Injection works and taking proactive measures to secure your website, you can significantly reduce the risk of exploitation. Whether you’re developing your own plugins or managing third-party ones, staying informed about potential vulnerabilities and applying security updates promptly is crucial. Remember, a well-secured site not only protects your data but also maintains the trust of your users.