CVE-2025-27801: The Episerver Content Management System (CMS) by Optimizely was affected by multiple Stored Cross-Site Scripting (XSS) vulnerabilities. This allowed a...

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. ContentReference properties, which could be used in the "Edit" section of the CMS, offered an upload functionality for documents. These documents could later be used as displayed content on the page. It was possible to upload SVG files that include malicious JavaScript code that would be executed if a user visited the direct URL of the preview image. 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)

Metrics

CVSS 3.1

4.8/10

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

CVSS 4.0

4.6/10

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:A/VC:N/VI:L/VA:L/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.33%

25.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

References

Timeline

Published: Jul 28, 2025
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2025-27801?

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. ContentReference properties, which could be used in the "Edit" section of the CMS, offered an upload functionality for documents. These documents could later be used as displayed content on the page. It was possible to upload SVG files that include malicious JavaScript code that would be executed if a user visited the direct URL of the preview image. 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)

How severe is CVE-2025-27801?

CVE-2025-27801 has a CVSS score of 4.6/10 (MEDIUM severity). The EPSS model estimates a 0.33% probability of exploitation in the next 30 days.

How do I fix CVE-2025-27801?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.