CVE-2026-64795: Cross-Site Scripting (XSS) Vulnerability

CVE-2026-64795 Overview

CVE-2026-64795 is a stored Cross-Site Scripting (XSS) vulnerability affecting Regular Labs extensions. Tag-provided custom HTML, module content and title overrides, and decoded modal or tooltip values fail to sanitize output before rendering. A content author with publishing privileges can inject JavaScript that executes in visitors' browsers.

The flaw is classified under CWE-79, Improper Neutralization of Input During Web Page Generation. Exploitation requires authenticated access to author content, but the payload executes against any visitor rendering the affected component.

Critical Impact
An authenticated content author can persist JavaScript that runs in the browser of every site visitor, enabling session theft, credential harvesting, and unauthorized actions performed under the victim's identity.

Affected Products

Regular Labs extensions with tag-processed custom HTML rendering
Regular Labs modules supporting content and title overrides
Regular Labs components rendering decoded modal or tooltip values

Discovery Timeline

2026-07-22 - CVE-2026-64795 published to NVD
2026-07-22 - Last updated in NVD database

Technical Details for CVE-2026-64795

Vulnerability Analysis

The vulnerability stems from three distinct output paths in Regular Labs extensions that render attacker-controlled data without HTML entity encoding. Tag-provided custom HTML accepts markup directly from content authors and passes it to the response body. Module content and title overrides substitute author-supplied values into templates without escaping. Decoded modal and tooltip values reverse HTML entity encoding before rendering, undoing any prior sanitization.

All three paths result in browser execution of author-supplied JavaScript. The vulnerability is stored, meaning the payload persists in the site's data store and fires whenever a visitor loads the affected page or interacts with the affected UI element.

Root Cause

The root cause is missing contextual output encoding in the render pipeline. The extensions treat trusted-role input as safe HTML rather than applying escaping appropriate to the rendering context. Where entity decoding occurs before output, prior sanitization is stripped, reintroducing script-capable markup.

Attack Vector

An authenticated content author submits a payload through a tag directive, module override field, or a value destined for a modal or tooltip. The payload includes script tags, event handler attributes such as onerror or onclick, or javascript: URIs. When any visitor renders the affected page, the browser parses and executes the injected script under the site's origin.

Verified exploit code is not published. See the Regular Labs Security Resources advisory for vendor-supplied technical details.

Detection Methods for CVE-2026-64795

Indicators of Compromise

Module content, module titles, or tag parameters containing <script>, onerror=, onload=, or javascript: substrings
Unexpected outbound requests from visitor browsers to attacker-controlled domains referenced from site pages
Modal and tooltip fields containing HTML-encoded entities that decode to executable markup such as <script>
Audit log entries showing content edits by author accounts immediately preceding visitor-reported anomalies

Detection Strategies

Scan content tables and module configuration for markup patterns matching script tags, inline event handlers, and javascript: URIs
Deploy a Content Security Policy in report-only mode to surface inline script violations originating from affected pages
Review web server access logs for repeated visitor requests followed by outbound connections to unfamiliar hosts
Correlate CMS author activity with client-side error telemetry to identify recently modified content that triggers script violations

Monitoring Recommendations

Alert on new or modified module overrides containing angle brackets, backticks, or encoded HTML entities
Monitor administrator and author account logins for unusual source IPs or session patterns
Track CSP violation reports for script-src and script-src-elem directives on public-facing pages
Enable file integrity monitoring on extension configuration files and template overrides

How to Mitigate CVE-2026-64795

Immediate Actions Required

Update all Regular Labs extensions to the latest patched release referenced in the vendor advisory
Audit existing module content, titles, tag parameters, modal fields, and tooltip values for injected markup
Revoke or reset credentials for content author accounts if any injected payloads are found
Restrict content authoring permissions to trusted users pending remediation

Patch Information

Refer to the Regular Labs Security Resources page for the fixed version numbers and release notes covering CVE-2026-64795. Apply updates across all sites where the affected extensions are installed.

Workarounds

Enforce a strict Content Security Policy that disallows inline scripts and restricts script-src to trusted origins
Disable or remove Regular Labs modules that expose custom HTML, override fields, or decoded modal or tooltip inputs until patched
Limit authoring privileges to accounts protected by multi-factor authentication
Introduce a reverse proxy or web application firewall rule that strips script tags and event handler attributes from author submissions

bash

# Example Content Security Policy header to limit XSS impact
Header set Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'self'; report-uri /csp-report"