# WebP Express <= 0.25.15 - Unauthenticated Stored Cross-Site Scripting via Alter HTML

- **ID:** WPSEC-2026-1254
- **Plugin:** WebP Express (`webp-express`), https://wordpress.org/plugins/webp-express/
- **Affected versions:** all versions before 0.25.16
- **Fixed in:** 0.25.16 (Update to 0.25.16 or later.)
- **Severity:** Medium 5.4 (CVSS:3.1/AV:N/AC:H/PR:N/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 2026-10-20)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/webp-express
- **Fix released:** 2026-10-18
- **Published:** 2026-10-20
- **URL:** https://wpsec.com/vuln/WPSEC-2026-1254/

## Description

The WebP Express plugin for WordPress is vulnerable to Stored Cross-Site Scripting and Denial of Service via the 'Alter HTML' image URL replacement feature in all versions up to, and including, 0.25.15, due to the bundled simple_html_dom parser restoring its internal '___noise___' placeholders into text and attribute values without escaping, and without rejecting input that already contains or forms such markers. This makes it possible for unauthenticated attackers to inject arbitrary web scripts through user-supplied content such as comments, which run whenever a user opens an affected page, or to make page rendering loop forever. Exploitation requires Alter HTML to be enabled in image URL replacement mode, which is not the default.

## References

- https://wpsec.com/vuln/WPSEC-2026-1254/
- https://plugins.svn.wordpress.org/webp-express/tags/0.25.16/
- https://wordpress.org/plugins/webp-express/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-1254/

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.