CVE-2026-4267 — johnbillion/query-monitor
MEDIUMCVE-2026-4267 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in johnbillion/query-monitor. A fix is available for johnbillion/query-monitor — see the affected versions and patch details below.
The Query Monitor plugin for WordPress has Reflected Cross-Site Scripting via Request URI
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-4267.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-4267 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
johnbillion/query-monitorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | johnbillion/query-monitor | all versions | 3.20.4composer require johnbillion/query-monitor:^3.20.4 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for johnbillion/query-monitor, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update johnbillion/query-monitor to 3.20.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-4267 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-4267 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-4267. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-4267 in your dependencies?
O3 Security finds CVE-2026-4267 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.