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Cross-site Scripting (XSS)Weakness · CWE-79

CVE-2026-5743

MEDIUM · 6.4 CVSS v3.1 Published 2026-07-11
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
70/100
Remediation priority · Elevated
Remotely reachable Zero-click 6 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

The SimpLy Gallery Block & Lightbox WordPress plugin (versions up to 3.3.3.2) contains a stored XSS vulnerability in the pgc_sgb_render_callback() function. The pgc_sgb_sanitize_custom_css() function uses a flawed regex that only removes quoted event handlers like onfocus="alert()" but fails to block unquoted handlers like onfocus=alert(document.cookie), allowing authenticated attackers with Author-level access to inject malicious scripts via the sliderMaxHeight block attribute.

MitigationUpdate to plugin version 3.3.4 or later which contains the corrected sanitization logic; until then, restrict Author-level user permissions and audit existing posts using the affected block.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check if SimpLy Gallery Block & Lightbox plugin is installed
    In WordPress admin, go to Plugins > Installed Plugins and look for 'SimpLy Gallery Block & Lightbox', or inspect the plugin directory /wp-content/plugins/simply-gallery-block/ for the main PHP file
    Affected if The plugin is installed and active in WordPress
  2. Verify the installed plugin version
    In the Plugins list page, check the version column for SimpLy Gallery Block & Lightbox, or open the main plugin PHP file and look for 'Version:' in the plugin header comment
    Affected if Version is 3.3.3.2 or lower (versions through 3.3.3.2 are vulnerable; 3.3.4 and later contain the fix)
  3. Identify if the gallery block with sliderMaxHeight attribute is in use
    Search your WordPress posts/pages content for '<!-- wp:sgb/' blocks (the gallery block), or query the wp_posts table for content containing 'sliderMaxHeight'
    Affected if Any published post contains the gallery block using the sliderMaxHeight attribute with a malicious payload
  4. Check for unquoted event handler injection in block attributes
    Inspect the raw block content in the database (wp_posts table) or use a block editor to view the gallery block settings; look for attributes like onfocus=alert() or other event handlers without quotes
    Affected if The sliderMaxHeight or any block attribute contains an unquoted event handler like onfocus=alert(document.cookie)

You are affected if the SimpLy Gallery Block & Lightbox plugin is installed at version 3.3.3.2 or lower AND any post contains the gallery block with a malicious unquoted event handler in the sliderMaxHeight or similar attribute.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update to plugin version 3.3.4 or later which contains the corrected sanitization logic; until then, restrict Author-level user permissions and audit existing posts using the affected block.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation3.0 h
  • Testing2.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,420
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-5743 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
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