HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content
Impact
The vulnerability occurs in configurations where foreign content is allowed, i.e. either svg or math are in the list of allowed elements.
Specifically, the requirements for the vulnerability are:
- Allowing one foreign element:
svg, ormath - Comments or one raw text element:
iframe,noembed,xmp,title,noframes,styleornoscript
Configurations that meet the above requirements plus the following are vulnerable to an additional vulnerability:
- Any HTML integration element:
title,desc,mi,mo,mn,ms,mtext,annotation-xml.
In case an application sanitizes user input with a vulnerable configuration, an attacker could bypass the sanitization and inject arbitrary HTML, including JavaScript code.
Note that in the default configuration the vulnerability is not present.
Patches
The vulnerability has been fixed in versions 8.0.723 and 8.1.722-beta (preview version).
Workarounds
Disallow foreign elements svg and math. This is the case in the default configuration, which is therefore not affected by the vulnerability.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| .NET (NuGet) | HtmlSanitizer | < 8.0.723, >= 8.1.0-beta, < 8.1.722-beta | 8.0.723, 8.1.722-beta |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-79- Platform
- .NET (NuGet)
- Package
HtmlSanitizer- Disclosed
- 04.10.2023
- Updated
- 11.10.2026 11:23
Sources and licenses
OSV / GitHub Advisory Database - GHSA-43cp-6p3q-2pc4 - CC BY 4.0
Vulnerability history: HtmlSanitizer
All published vulnerabilities of this package (.NET (NuGet)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 3
- First → latest
- 01.2021 02.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Medium 2
- Low 1
Disclosures per year
- 2021: 1
- 2022: 0
- 2023: 1
- 2024: 0
- 2025: 0
- 2026: 1
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HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content this entry
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