CVE-2023-44390: HtmlSanitizer vulnerable to Cross-site Scripting in Foreign Content

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-10-05 · updated 2026-06-17
Weakness: CWE-79

Description

HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. The vulnerability occurs in configurations where foreign content is allowed, i.e. either `svg` or `math` are in the list of allowed elements. In the 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. The vulnerability has been fixed in versions 8.0.723 and 8.1.722-beta (preview version).

Affected products

mganss HtmlSanitizer: before 8.0.723; 8.1.719-beta — fixed in 8.0.723

How to fix

Upgrade to a fixed version: mganss HtmlSanitizer 8.0.723. Check the vendor advisory for mitigations.

References

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