Mixed Media Gallery Blocks <= 3.3.3.1 - Authenticated (Author+) Stored Cross-Site Scripting via sliderMaxHeight Block Attribute

Summary

The SimpLy Gallery Block & Lightbox plugin for WordPress is vulnerable to Stored Cross-Site Scripting via block attributes in all versions up to, and including, 3.3.3.2. This is due to insufficient input sanitization and output escaping on the sliderMaxHeight block attribute in the pgc_sgb_render_callback() function. The vulnerability exists because the pgc_sgb_sanitize_custom_css() function uses a flawed regex pattern that only removes event handlers with quoted values (e.g., onfocus="alert()") but fails to catch unquoted event handlers (e.g., onfocus=alert(document.cookie)), allowing the malicious code to bypass sanitization. This makes it possible for authenticated attackers, with Author-level access and above, to inject arbitrary web scripts in pages via block attributes that will execute whenever a user accesses an injected page.

Timeline

1. Jul 11, 2026, 2:31 AM UTCCVE published
2. Jul 13, 2026, 2:34 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Jul 13, 2026, 2:40 PM UTCRecord last updated

Affected versions

• gallerycreator SimpLy Gallery

  through 3.3.3.1

References 10