CVE-2026-100370

01/Description

DOMSanitizer is a DOM/SVG/MathML Sanitizer for PHP 7.3+. Prior to version 1.0.15, the isDangerousUrl() method is responsible for rejecting dangerous URL values in the href and xlink:href attributes. The weakness is that "javascript:" is rejected as a scheme, while "data:" is rejected only when the literal substring onload appears in the URL value (/^data:.*onload/i). Because data: payloads are routinely Base64-encoded, the dangerous content (<script>, event handlers, etc.) is invisible to that substring test. A URL such as data:text/html;base64,… therefore survives in href / xlink:href, even though the decoded payload is active markup. This is an incomplete input-validation / sanitization defect in the sanitizer itself. This issue has been patched in version 1.0.15.

02/References5

• github.com/rhukster/dom-sanitizer/commit/10f97807e4501d60f63987…
• github.com/rhukster/dom-sanitizer/commit/fb8f758b41134fc5fb2f56…
• github.com/rhukster/dom-sanitizer/releases/tag/1.0.15
• github.com/rhukster/dom-sanitizer/security/advisories/GHSA-wcj2…
• github.com/rhukster/dom-sanitizer/security/advisories/GHSA-wcj2…