CVE-2026-54570
AngleSharp is a .NET library for parsing angle bracket based hyper-texts. Prior to 1.5.0, MathAnnotationXmlElement in AngleSharp/Mathml/Dom/Internal/MathAnnotationXmlElement.cs is not treated as an HTML integration point when its encoding attribute is text/html or application/xhtml+xml, causing Consume in AngleSharp/Html/Parser/HtmlDomBuilder.cs to route tokens through foreign-content parsing instead of HTML parsing. A sanitizer can therefore observe a different DOM from the browser that reparses the serialized output. An attacker can combine this namespace differential with markup-breaking characters in an attribute value so that an element hidden from the sanitizer becomes active script-capable HTML after browser reparse, resulting in mutation cross-site scripting. This issue is fixed in version 1.5.0.
- CVSS v3.1
- 6.9 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N - CVSS v3.1
- 6.9 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:H/A:N - EPSS
- 0.25% chance of exploitation in the next 30 days, 16th percentile
- Published
- 2026-08-18