CVE-2026-61784: Cstigler Node-Xhtml-Purifier

Medium severity, CVSS 6.1. EPSS: 0.2% chance of exploitation in the next 30 days.

xhtml-purifier is a Node.js library to take in raw/unknown/untrusted HTML and output cleaned, purified, trusted HTML. Versions prior to 0.4.3 do not HTML-entity-encode attribute values when serializing its sanitized output. In attributeString() (XHTMLPurifier.js, around line 148) the attribute value is concatenated directly into a double-quoted attribute without encoding. As a result, an attacker-controlled value in any allowed attribute (class, style, title, alt, src, href) can include a double-quote character to break out of the attribute and inject an additional attribute, such as a JavaScript event handler (for example onmouseover or onerror). The injected handler survives sanitization and executes when the output is rendered, which is a sanitizer bypass leading to cross-site scripting. The fix in version 0.4.3 HTML-entity-encodes attribute values before serialization.

Affected products

• Cstigler Node-Xhtml-Purifier: before 0.4.3 (fixed in 0.4.3)

Published 2026-09-24. Last modified 2026-09-30.