CVE-2020-26293
Possible XSS bypass if style tag is allowed
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
Possible XSS bypass if style tag is allowed
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.
- Record
CVE-2020-26293- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N - Weakness
- CWE-74
- Updated
- 2026-11-02
EUVDEUVD-2021-0498
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.
- Record
EUVD-2021-0498- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-8j9v-h2vp-2hhv
XSS in HtmlSanitizer
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.
- Record
GHSA-8j9v-h2vp-2hhv- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N - Weakness
- CWE-74, CWE-79
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2020-26293- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N - CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-74, CWE-79
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2020-26293- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVGHSA-8j9v-h2vp-2hhv
XSS in HtmlSanitizer
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.
- Record
GHSA-8j9v-h2vp-2hhv- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:N/I:H/A:N - Weakness
- CWE-74, CWE-79
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
HtmlSanitizerNuGet |
before 5.0.372 | 5.0.372 |
HtmlSanitizerNuGet |
before 5.0.372, plus listed versions 1.0.4925.298151.0.4927.308731.1.5243.284481.1.5297.284031.1.5338.17998 Show 45 moreShow less2.0.5449.205502.0.5548.249322.0.5595.221832.0.5595.303252.0.5623.304652.0.5735.242963.0.5781.31354-beta3.0.66-beta3.1.67-beta3.1.75-beta3.1.763.1.793.1.913.1.933.1.983.2.100-beta3.2.1033.2.1053.2.96-beta3.3.122-beta3.3.125-beta3.3.126-beta3.3.127-beta3.3.128-beta3.3.129-beta3.3.130-beta3.3.131-beta3.3.132-beta3.3.1423.3.143-beta3.3.144-beta3.3.145-beta3.3.146-beta3.3.147-beta3.3.148-beta3.4.152-beta3.4.1563.5.168-beta3.5.169-beta4.0.1794.0.1804.0.1814.0.1824.0.1834.0.185 |
5.0.372 |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2020-26293 is a medium vulnerability (CVSS 6.1) in Htmlsanitizer Project Htmlsanitizer, published January 4, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.01%, the 63rd percentile. Fixed in HtmlSanitizer 5.0.372.
References
github.com/mganss/HtmlSanitizer/security/advisories/GHSA-8j9v-h2vp-2hhv
nuget.org/packages/HtmlSanitizer
nvd.nist.gov/vuln/detail/CVE-2020-26293
Left out here: 23 versions. The JSON record has them.