CVE-2025-27802: XSS (CVSS 4.8)

Description

The Episerver Content Management System (CMS) by Optimizely was affected by multiple Stored Cross-Site Scripting (XSS) vulnerabilities. This allowed an authenticated attacker to execute malicious JavaScript code in the victim's browser. RTE properties (text fields), which could be used in the "Edit" section of the CMS, allowed the input of arbitrary text. It was possible to input malicious JavaScript code in these properties that would be executed if a user visits the previewed page. Attackers needed at least the role "WebEditor" in order to exploit this issue. Affected products: Version 11.X: EPiServer.CMS.Core (<11.21.4) with EPiServer.CMS.UI (<11.37.5), Version 12.X: EPiServer.CMS.Core (<12.22.1) with EPiServer.CMS.UI (<11.37.3)

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CVSS v3.1 Score

4.8

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:N

Weakness Type (CWE)

CWE-79 Cross-site Scripting (XSS)

References

Other References

https://api.nuget.optimizely.com/packages/episerver.cms.core/11.21.4# https://api.nuget.optimizely.com/packages/episerver.cms.core/12.22.1# https://r.sec-consult.com/optimizely http://seclists.org/fulldisclosure/2025/Aug/18

Frequently Asked Questions

What is CVE-2025-27802? +

The Episerver Content Management System (CMS) by Optimizely was affected by multiple Stored Cross-Site Scripting (XSS) vulnerabilities. This allowed an authenticated attacker to execute malicious JavaScript code in the victim's browser. RTE properties (text fields), which could be used in the "Edit" section of the CMS, allowed the input of arbitrary text. It was possible to input malicious JavaScript code in these properties that would be executed if a user visits the previewed page. Attackers needed at least the role "WebEditor" in order to exploit this issue. Affected products: Version 11.X: EPiServer.CMS.Core (<11.21.4) with EPiServer.CMS.UI (<11.37.5), Version 12.X: EPiServer.CMS.Core (<12.22.1) with EPiServer.CMS.UI (<11.37.3) It has a CVSS v3.1 base score of 4.8 (MEDIUM).

How severe is CVE-2025-27802? +

CVE-2025-27802 has a CVSS v3.1 score of 4.8 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

How do I check if I'm vulnerable to CVE-2025-27802? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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