# Newsletters <= 4.18.1 - Unauthenticated PHP Object Injection via Database Update Notice Dismissal

- **ID:** WPSEC-2026-1338
- **Plugin:** Newsletters (`newsletters-lite`), https://wordpress.org/plugins/newsletters-lite/
- **Affected versions:** all versions before 4.18.2
- **Fixed in:** 4.18.2 (Update to 4.18.2 or later.)
- **Severity:** High 8.1 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H)
- **Weakness:** CWE-502
- **Usage among sites WPSec scans:** plugin Low, affected versions Low (as of 2026-10-21)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/newsletters-lite
- **Fix released:** 2026-10-20
- **Published:** 2026-10-21
- **URL:** https://wpsec.com/vuln/WPSEC-2026-1338/

## Description

The Newsletters plugin for WordPress is vulnerable to PHP Object Injection via the 'version' parameter of the database update notice dismissal ('hidemessage') handler in all versions up to, and including, 4.18.1, due to the handler running on the init hook with no capability check or nonce, storing the value in the 'hidedbupdate' option, and the plugin passing that stored value through maybe_unserialize() again when it reads it back. This makes it possible for unauthenticated attackers to inject a PHP object. No known POP chain is present in the vulnerable software. If a POP chain is present via an additional plugin or theme installed on the target system, it could allow the attacker to delete arbitrary files, retrieve sensitive data, or execute code.

## References

- https://wpsec.com/vuln/WPSEC-2026-1338/
- https://plugins.svn.wordpress.org/newsletters-lite/tags/4.18.2/
- https://wordpress.org/plugins/newsletters-lite/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-1338/

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.