# Sign-up Sheets <= 2.4.0 - Reflected Cross-Site Scripting via Sign-up Link

- **ID:** WPSEC-2026-2279
- **Plugin:** Sign-up Sheets (`sign-up-sheets`), https://wordpress.org/plugins/sign-up-sheets/
- **Affected versions:** all versions before 2.4.1
- **Fixed in:** 2.4.1 (Update to 2.4.1 or later.)
- **Severity:** Medium 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N)
- **Weakness:** CWE-79
- **Usage among sites WPSec scans:** plugin Low, affected versions None seen (as of 2026-11-03)
- **Attack surface analysis:** https://attacksurface.wpsec.com/plugin/sign-up-sheets
- **Fix released:** 2026-10-31
- **Published:** 2026-11-03
- **URL:** https://wpsec.com/vuln/WPSEC-2026-2279/

## Description

The Sign-up Sheets plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the request URL used to build the "Sign up" link on public sign-up sheet pages in all versions up to, and including, 2.4.0. This is due to insufficient output escaping: the current URL is passed through esc_url() before add_query_arg() is applied, and add_query_arg() decodes and re-emits the query string keys without encoding them. This makes it possible for unauthenticated attackers to inject arbitrary web scripts that run in a user's browser if they can trick the user into clicking a crafted link.

## References

- https://wpsec.com/vuln/WPSEC-2026-2279/
- https://plugins.svn.wordpress.org/sign-up-sheets/tags/2.4.1/
- https://wordpress.org/plugins/sign-up-sheets/

Source: WPSec, https://wpsec.com/vuln/WPSEC-2026-2279/

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.