CVE-2025-27801 – Optimizely Episerver Stored Cross-Site Scripting (XSS) Vulnerability

CVE ID : CVE-2025-27801

Published : July 28, 2025, 9:15 a.m. | 2 hours, 3 minutes ago

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 (
Severity: 4.8 | MEDIUM

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