What’s Vulnerable › Vulnerabilities

CVE-2020-26293: Possible XSS bypass if style tag is allowed

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.0% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-01-04 · updated 2026-06-17
• Weakness: CWE-74

Description

HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. In HtmlSanitizer before version 5.0.372, there is a possible XSS bypass if style tag is allowed. If you have explicitly allowed the `<style>` tag, an attacker could craft HTML that includes script after passing through the sanitizer. The default settings disallow the `<style>` tag so there is no risk if you have not explicitly allowed the `<style>` tag. The problem has been fixed in version 5.0.372.

Affected products

• mganss HtmlSanitizer: before 5.0.372 — fixed in 5.0.372

How to fix

Upgrade to a fixed version: mganss HtmlSanitizer 5.0.372. Check the vendor advisory for mitigations.

References

• https://github.com/mganss/HtmlSanitizer/commit/a3a7602a44d4155d51ec0fbbedc2a49e9c7e2eb8
• https://github.com/mganss/HtmlSanitizer/releases/tag/v5.0.372
• https://github.com/mganss/HtmlSanitizer/security/advisories/GHSA-8j9v-h2vp-2hhv
• https://www.nuget.org/packages/HtmlSanitizer/
• https://github.com/mganss/HtmlSanitizer/commit/a3a7602a44d4155d51ec0fbbedc2a49e9c7e2eb8
• https://github.com/mganss/HtmlSanitizer/releases/tag/v5.0.372
• https://github.com/mganss/HtmlSanitizer/security/advisories/GHSA-8j9v-h2vp-2hhv
• https://www.nuget.org/packages/HtmlSanitizer/

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