GitHub Advisoryadvisory · npm

GHSA-j8r4-32c5-33rc xhtml-purifier has HTML attribute-injection (sanitizer bypass) that leads to XSS

MEDIUM Published 2026-09-24 Modified 2026-09-24 Official page ↗
Aliases
CVE-2026-61784
Ecosystem
npm
Packages
xhtml-purifier
Severity
Moderate
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Weaknesses
CWE-116, CWE-79
Reviewed
2026-09-24

Affected packages

• npm xhtml-purifier: < 0.4.3 → fixed in 0.4.3

Description

xhtml-purifier does 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 HTML-entity-encodes attribute values before serialization.

Related

Alias · CVE (1)

  • CVE-2026-61784 xhtml-purifier is a Node.js library to take in raw/unknown/untrusted HTML and output cleaned, purified, trusted HTML. vulnerability

Weakness · CWE (2)

  • CWE-116 Improper Encoding or Escaping of Output weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation weakness

References