What is Privilege Escalation Vulnerability?

Privilege Escalation occurs when a lower-privileged or unauthenticated user can perform an action that escalates their current privilege to a higher level. These vulnerabilities allow attackers to gain elevated access to a website, enabling them to perform actions typically restricted to administrators or other high-privilege users. A common example is when unauthenticated users exploit a vulnerability to log in as an administrator.

The severity of these vulnerabilities is extremely high, especially when they allow attackers to escalate their privileges to an admin level. When this happens, the entire website can be fully compromised.

What Causes a Privilege Escalation (Priv. Esc) Vulnerability?

Privilege Escalation vulnerabilities arise from improper management of user roles and permissions. Some common causes include:

• Incorrect Permission Checks: WordPress has a built-in system for managing user roles and capabilities. A Priv. Esc. vulnerability occurs when a plugin incorrectly checks or bypasses these capabilities, allowing lower-privileged users to perform administrative actions.
• Flawed Access Control Logic: Plugins can mismanage user roles and permissions, especially during updates or custom code development. This often happens when user permissions aren’t strictly controlled during sensitive operations, such as creating posts, editing settings, or managing files.
• Insecure Use of wp_ajax_ Hooks: Developers sometimes expose sensitive administrative functions to non-admin users through insecure AJAX calls.

Privilege escalation vulnerabilities often appear in plugins that provide alternative login functionality, such as social media login. If this login process isn’t properly validated, attackers can bypass authentication and log in as any user. This is often due to functions like wp_set_auth_cookie() or wp_set_current_user, which can be improperly handled.

What Can Happen If Your WordPress Website Has a Priv. Esc. Vulnerability?

The impact depends on how far the privilege can be escalated. In most cases, exploited privilege escalation vulnerabilities allow attackers to gain administrative access. This means that the hacker can install fake plugins to add backdoors, gaining complete control of the website.

Once hackers have inserted a backdoor into the site, they typically use it to:

• Steal sensitive information stored in the database or filesystem (media, documents, files, etc.).
• Inject SEO spam and redirect the website to scam or malicious sites.
• Host malware and phishing pages.
• Use the website as part of a botnet to attack other websites.

A notable example of a recent Privilege Escalation vulnerability occurred in the LiteSpeed Cache plugin, which was patched in late August 2024. This vulnerability allowed unauthenticated attackers to gain administrator access and was mass-exploited soon after it was disclosed. The security researcher who discovered the issue was awarded a $14,400 bounty by Patchstack. You can read more about it here.

How Can WordPress Developers Prevent Priv. Esc. Vulnerabilities?

Each Privilege Escalation scenario is unique, so there is no one-size-fits-all solution to avoid these vulnerabilities. However, developers should ensure that:

• Proper Authentication is Implemented: Validate authentication before making any calls to WordPress functions that allow users to log in as a specific user or access restricted features.

Since Privilege Escalation often overlaps with broken access control vulnerabilities, it’s highly recommended to read our earlier post on this topic: https://theadminbar.com/security-weekly/what-is-a-broken-access-control-vulnerability/.

For website developers and administrators:

• Monitor Plugin Vulnerabilities: Regularly check for vulnerabilities reported in the plugins you use, especially those related to Privilege Escalation.
• Prioritize Critical Fixes: Prioritize addressing vulnerabilities that allow the lowest level of privilege (such as unauthenticated visitors) to escalate to the highest privilege level (administrator). These should be treated as urgent threats.

Conclusion

Privilege Escalation vulnerabilities pose a serious risk to WordPress websites, potentially giving attackers full control over the site. These vulnerabilities can lead to data theft, malware distribution, and complete site compromise.

Both plugin developers and website owners need to stay vigilant for plugin vulnerabilities, and put extra attention on privilege escalation vulnerabilities which can turn unauthenticated users into admins.