Skip to content

The Query Monitor plugin for WordPress has Reflected Cross-Site Scripting via Request URI

Moderate severity GitHub Reviewed Published Mar 19, 2026 in johnbillion/query-monitor • Updated Mar 19, 2026

Package

composer johnbillion/query-monitor (Composer)

Affected versions

< 3.20.4

Patched versions

3.20.4

Description

Impact

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.

Patches

This issue has been patched in Query Monitor 3.20.4.

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.

References

@johnbillion johnbillion published to johnbillion/query-monitor Mar 19, 2026
Published to the GitHub Advisory Database Mar 19, 2026
Reviewed Mar 19, 2026
Last updated Mar 19, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS score

Weaknesses

Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS)

The product receives input from an upstream component, but it does not neutralize or incorrectly neutralizes special characters such as <, >, and & that could be interpreted as web-scripting elements when they are sent to a downstream component that processes web pages. Learn more on MITRE.

CVE ID

CVE-2026-4267

GHSA ID

GHSA-2xr4-chcf-vmvf
Loading Checking history
See something to contribute? Suggest improvements for this vulnerability.