# WP Meteor Website Speed Optimization Addon <= 3.4.18 - Authenticated (Contributor+) Stored Cross-Site Scripting via onload/onerror Attribute Rewriting

- **ID:** WPSEC-2026-0467
- **Plugin:** WP Meteor Website Speed Optimization Addon (`wp-meteor`), https://wordpress.org/plugins/wp-meteor/
- **Affected versions:** from 3.0.6 before 3.4.19
- **Fixed in:** 3.4.19 (Update to 3.4.19 or later.)
- **Severity:** Medium 6.4 (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N)
- **Weakness:** CWE-79
- **Usage among sites WPSec scans:** plugin Medium, affected versions Medium (as of 2026-10-06)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/wp-meteor
- **Fix released:** 2026-10-03
- **Published:** 2026-10-06
- **URL:** https://wpsec.com/vuln/WPSEC-2026-0467/

## Description

The WP Meteor Website Speed Optimization Addon plugin for WordPress is vulnerable to Stored Cross-Site Scripting via its output-buffer rewriting of onload and onerror handlers on html, body, img and iframe tags in all versions up to, and including, 3.4.18. This is due to a naive regular expression that also rewrites ' onload=' or ' onerror=' text found inside quoted attribute values and inserts a double-quoted handler string there. Because the attacker's text is only an attribute value when it is saved, it passes kses filtering. The rewrite then lets it break out of the attribute and become a real event handler. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.

## References

- https://wpsec.com/vuln/WPSEC-2026-0467/
- https://plugins.svn.wordpress.org/wp-meteor/tags/3.4.19/
- https://wordpress.org/plugins/wp-meteor/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-0467/

License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Free to use, share and adapt, also commercially, if you credit WPSec and link to this advisory.