CVE-2026-4267

Credits

Many thanks to Dmitrii Ignatyev at CleanTalk for responsibly disclosing this vulnerability.

How can I report a security bug?

You can submit a private security vulnerability report to Query Monitor via the Security tab on the GitHub repo. The GitHub Security Advisory process facilitates private collaboration on security issues. You'll receive credit for a valid report and a CVE if necessary.

The Query Monitor plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the $_SERVER['REQUEST_URI'] parameter in all versions up to, and including, 3.20.3 due to insufficient output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick an Administrator-level user into performing an action such as clicking on a link.

On admin requests, the plugin reads user controlled data from $_SERVER['REQUEST_URI'] and stores it in the request field, then renders request, matched_query, and query_string through format_url(). If the attacker supplied string does not contain &, format_url() returns it without HTML escaping, which allows injected HTML or JavaScript from the request target to be inserted directly into the page inside a <code> element and executed in the victim's browser.

CVE-2026-4267 has a CVSS score of 6.1 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.20.4); upgrading removes the vulnerable code path.

Kodem intelligence

This issue has been patched in Query Monitor 3.20.4.

1. What is CVE-2026-4267? CVE-2026-4267 is a medium-severity security vulnerability in johnbillion/query-monitor (composer), affecting versions < 3.20.4. It is fixed in 3.20.4.
2. How severe is CVE-2026-4267? CVE-2026-4267 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of johnbillion/query-monitor are affected by CVE-2026-4267? johnbillion/query-monitor (composer) versions < 3.20.4 is affected.
4. Is there a fix for CVE-2026-4267? Yes. CVE-2026-4267 is fixed in 3.20.4. Upgrade to this version or later.
5. Is CVE-2026-4267 exploitable, and should I be worried? Whether CVE-2026-4267 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-4267 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-4267? Upgrade johnbillion/query-monitor to 3.20.4 or later.