Add Custom CSS and JS <= 1.20 - Cross-Site Request Forgery to Stored Cross-Site Scripting
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- Add Custom CSS and JS
- Affected Version
<= 1.20- CVSS
- 6.1Medium
- Weakness type
- CWE-352 · Cross-Site Request Forgery (CSRF)
- CVE
CVE-2024-3903
At a glance
CVE-2024-3903 is a medium-severity Cross-Site Request Forgery (CSRF) vulnerability in the Add Custom CSS and JS WordPress plugin, affecting versions <= 1.20. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed April 2024, reported by Bob Matyas.
Vulnerability Overview
The Add Custom CSS and JS plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 1.20. This is due to missing or incorrect nonce validation on the custom_js_css page. This makes it possible for unauthenticated attackers to modify plugin settings and inject malicious web scripts via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no privileges on the target site.
CWE-352: Cross-Site Request Forgery (CSRF)
Reaching this weakness in Add Custom CSS and JS <= 1.20 takes a caller who can reach the endpoint. Cross-site request forgery abuses the fact that browsers attach a victim's cookies to any request, so a state-changing action that only checks who you are, not whether you meant to act, can be triggered from another site.
An attacker who gets a logged-in user to load a crafted page can perform that action as them, with the impact scaling to whatever the victim's role is allowed to do. No fixed build of this plugin is recorded for Add Custom CSS and JS yet, so installs running <= 1.20 stay exposed until the vendor ships one.
Remediation
No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
How does WordSec protect against this?
The attempt arrives as an ordinary request to Add Custom CSS and JS: WordSec's web application firewall inspects request payloads before WordPress loads them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C