CVE-2026-18742
Deferred Deferred - Pending Action

Stored XSS in Flatsome WordPress Theme via Custom HTML Block

Publication date: 2026-11-14

Last updated on: 2026-11-14

Assigner: Wordfence

Description
The Flatsome theme for WordPress is vulnerable to Stored Cross-Site Scripting via 'data-text-sec', 'data-title', and 'title' Attributes via Custom HTML Block in all versions up to, and including, 3.20.12 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The payload survives server-side sanitization because wp_kses_post permits data-* attributes globally via _wp_add_global_attributes, allowing attacker-controlled values in data-text-sec, data-title, and title attributes to persist in saved post content and be later interpreted as HTML by the ux-countdown, scroll-to, and lightbox-gallery JavaScript behaviors.

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Meta Information

Published
2026-11-14
Last Modified
2026-11-14
Generated
2026-11-15
AI Q&A
2026-11-14
EPSS Evaluated
N/A
NVD
CVE-2026-18742
EUVD
EUVD-2026-125891

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
UX-themes Flatsome From 0 (inc) to 3.20.12 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-79 The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

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Executive Summary

The Flatsome WordPress theme has a stored Cross-Site Scripting (XSS) vulnerability in versions up to 3.20.12. It allows authenticated attackers with contributor-level access or higher to inject malicious scripts via data-text-sec, data-title, and title attributes in the Custom HTML Block. The issue occurs because input sanitization is insufficient and output escaping fails, letting malicious scripts persist in saved posts. These scripts execute when users access the infected pages.

Detection Guidance

Check WordPress installations for the Flatsome theme versions up to 3.20.12. Inspect Custom HTML blocks for injected scripts in data-text-sec, data-title, or title attributes. Review saved posts for unexpected HTML content in these attributes.

Impact Analysis

If you use the vulnerable Flatsome theme, attackers could steal user sessions, redirect to malicious sites, or perform actions on your behalf. Visitors to your site may have their data compromised or be exposed to further attacks. The impact depends on the attacker's goals and your site's user base.

Compliance Impact

This vulnerability could lead to data breaches, violating GDPR and HIPAA requirements for protecting user data. If personal or sensitive data is exposed due to the XSS attack, organizations may face fines, legal action, and reputational damage. Compliance depends on how the vulnerability is exploited and the data involved.

Mitigation Strategies

Update the Flatsome theme to the latest version beyond 3.20.12. Remove any suspicious Custom HTML blocks containing data-text-sec, data-title, or title attributes with script content. Implement stricter input validation for HTML attributes in WordPress.

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