CVE-2025-27801 Stored Cross-Site Scripting in Episerver Content Management System (CMS) Media Selection Preview
Authenticated attackers can execute malicious JavaScript via uploaded SVG files in the Episerver CMS media preview, requiring a WebEditor role.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-27801?
CVE-2025-27801 is a medium-severity cross-site scripting vulnerability in Optimizely Episerver Content Management System (CMS), published on 28 Jul 2025. An attacker needs administrator access to exploit it, and only if a user opens a file or follows a link.
Official 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)
Weakness: CWE-79
Which versions are affected by CVE-2025-27801?
How do I fix CVE-2025-27801?
No fix has been published for CVE-2025-27801 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2025-27801 being exploited?
There is no known exploitation of CVE-2025-27801 in the wild and no public exploit code.
Sources
Also known as GHSA-c873-fj46-wp48.