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CVE-2026-25543— HtmlSanitizer has a bypass via template tag

Quick assessment

Affected
mganss HtmlSanitizer
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

HTMLSanitizer是JuliaHub开源的一个HTML格式化软件。 HTMLSanitizer 9.0.892之前版本和9.1.893-beta之前版本存在安全漏洞，该漏洞源于允许template标签时未清理其内容，可能导致跨站脚本攻击。

AI Predicted 5.4 Difficulty: Moderate EPSS 0.28% · P20

Possible ATT&CK Techniques 1 AI

T1189 · Drive-by Compromise
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I. Basic Information for CVE-2026-25543

Vulnerability Information
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Vulnerability Title
HtmlSanitizer has a bypass via template tag
Source: CVE Program / CVE List V5
Vulnerability Description
HtmlSanitizer is a .NET library for cleaning HTML fragments and documents from constructs that can lead to XSS attacks. Prior to versions 9.0.892 and 9.1.893-beta, if the template tag is allowed, its contents are not sanitized. The template tag is a special tag that does not usually render its contents, unless the shadowrootmode attribute is set to open or closed. This issue has been patched in versions 9.0.892 and 9.1.893-beta.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
对输出编码和转义不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
HTMLSanitizer 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
HTMLSanitizer是JuliaHub开源的一个HTML格式化软件。 HTMLSanitizer 9.0.892之前版本和9.1.893-beta之前版本存在安全漏洞，该漏洞源于允许template标签时未清理其内容，可能导致跨站脚本攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mganss HtmlSanitizer < 9.0.892 -

II. Public POCs for CVE-2026-25543

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III. Intelligence Information for CVE-2026-25543

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IV. Related Vulnerabilities

Same product: HtmlSanitizer
Same vendor: mganss
Same weakness: CWE-116