# Meta Box - WordPress Custom Fields Framework <= 5.15.2 - Authenticated (Contributor+) Stored Cross-Site Scripting via Block Editor Field

- **ID:** WPSEC-2026-1301
- **Plugin:** Meta Box – A Framework for Dynamic Websites (`meta-box`), https://wordpress.org/plugins/meta-box/
- **Affected versions:** from 5.11.0 before 5.15.3
- **Fixed in:** 5.15.3 (Update to 5.15.3 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 Low, affected versions Low (as of 2026-10-21)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/meta-box
- **Fix released:** 2026-10-20
- **Published:** 2026-10-21
- **URL:** https://wpsec.com/vuln/WPSEC-2026-1301/

## Description

The Meta Box plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the block_editor field type in all versions up to, and including, 5.15.2 due to the field value being saved without any sanitization, even for users lacking the unfiltered_html capability. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts into a block_editor custom field that execute whenever a user accesses a page where the field is rendered. Exploitation requires a block_editor field to be registered on content the attacker can edit.

## References

- https://wpsec.com/vuln/WPSEC-2026-1301/
- https://plugins.svn.wordpress.org/meta-box/tags/5.15.3/
- https://wordpress.org/plugins/meta-box/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-1301/

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.