# Popup Builder <= 4.4.5 - Unauthenticated Stored Cross-Site Scripting via Subscription Form Name Fields

- **ID:** WPSEC-2026-1351
- **Plugin:** Popup Builder – Create highly converting, mobile friendly marketing popups. (`popup-builder`), https://wordpress.org/plugins/popup-builder/
- **Affected versions:** from 4.1.1 before 4.4.6
- **Fixed in:** 4.4.6 (Update to 4.4.6 or later.)
- **Severity:** High 7.2 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N)
- **Weakness:** CWE-79
- **Usage among sites WPSec scans:** plugin High, affected versions Medium (as of 2026-10-21)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/popup-builder
- **Fix released:** 2026-10-19
- **Published:** 2026-10-21
- **URL:** https://wpsec.com/vuln/WPSEC-2026-1351/

## Description

The Popup Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the subscription form first name and last name fields in versions 4.1.1 through 4.4.5, due to insufficient input sanitization and output escaping. Names were stored after sanitize_text_field() only, which keeps a '<' followed by whitespace, and were printed on the admin Subscribers page through wp_kses() with an allowlist that permits script tags and onclick attributes, so the stored text becomes a real tag again. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that execute when an administrator views the Subscribers page.

## References

- https://wpsec.com/vuln/WPSEC-2026-1351/
- https://plugins.svn.wordpress.org/popup-builder/tags/4.4.6/
- https://wordpress.org/plugins/popup-builder/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-1351/

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.