How severe is CVE-2020-26293?

CVE-2020-26293 has a CVSS score of 6.1/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-26293?

CVE-2020-26293 affects the following packages: HtmlSanitizer (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2020-26293?

Update HtmlSanitizer to 5.0.372 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26293 is resolved across your whole dependency graph.

How do I detect CVE-2020-26293 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2020-26293 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2020-26293 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-26293 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-26293?

CVE-2020-26293 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 63th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-26293?

CVE-2020-26293 is classified as CWE-74 (CWE-74), Cross-site Scripting (XSS) (CWE-79). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2020-26293 published, and has it been updated?

CVE-2020-26293 was published on January 4, 2021 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

MEDIUM severity

CVE-2020-26293 — HtmlSanitizer

MEDIUMFix: mganss/HtmlSanitizer@a3a7602

CVE-2020-26293 is a medium-severity (CVSS 6.1) CWE-74 vulnerability in HtmlSanitizer. A fix is available for HtmlSanitizer — see the affected versions and patch details below.

XSS in HtmlSanitizer

Also known asGHSA-8j9v-h2vp-2hhv

Published

Jan 4, 2021

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 31, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs63th percentile — riskier than 63% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

1 pkg affected

.NETHtmlSanitizer

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

Impact

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.

Patches

The problem has been fixed in version 5.0.372.

Workarounds

Remove the <style> tag from the set of allowed tags.

For more information

If you have any questions or comments about this advisory open an issue in https://github.com/mganss/HtmlSanitizer

Credits

This issue was discovered by Michal Bentkowski of Securitum.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`HtmlSanitizer`	all versions	5.0.372`dotnet add package HtmlSanitizer --version 5.0.372`

Affected Products

1 product · 1 configurations

Application

htmlsanitizerhtmlsanitizer_project

< 5.0.372

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for HtmlSanitizer, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update HtmlSanitizer to 5.0.372 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-26293 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact 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. ### Patches The problem has been fixed in version 5.0.372. ### Workarounds Remove the `<style>` tag from the set of allowed tags. ### For more information If you have any questions or comments about this advisory open an issue in https://github.com/mganss/HtmlSanitizer ### Credits This issue was discovered by Michal Ben