CVE-2025-0747: Thesamur Embedai XSS Vulnerability

CVE-2025-0747 Overview

CVE-2025-0747 is a stored cross-site scripting (XSS) vulnerability in EmbedAI, an application developed by thesamur. An authenticated attacker can inject malicious JavaScript into a chat message. The payload executes in the browser of any user who later opens the affected chat. The flaw is tracked under CWE-79 (Improper Neutralization of Input During Web Page Generation).

The issue was disclosed through an INCIBE Security Notice covering multiple vulnerabilities in EmbedAI.

Critical Impact
Authenticated attackers can execute arbitrary JavaScript in the browsers of other EmbedAI users, enabling session theft, credential harvesting, and further account compromise.

Affected Products

Thesamur EmbedAI (all versions covered by CPE cpe:2.3:a:thesamur:embedai:*:*:*:*:*:*:*:*)
Web-based chat interface component of EmbedAI
Any deployment exposing multi-user chat functionality

Discovery Timeline

2025-01-30 - CVE-2025-0747 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-0747

Vulnerability Analysis

EmbedAI stores user-supplied chat messages and later renders them to other participants without adequate output encoding or input sanitization. When an authenticated user submits a message containing HTML or JavaScript, the payload is persisted server-side. Any subsequent viewer who opens the chat causes the browser to parse and execute the injected script in the context of the EmbedAI origin.

Because the payload is stored rather than reflected, exploitation does not require a crafted link or repeated social engineering. A single injection persists until the record is purged. User interaction is limited to opening the chat, which is a routine action.

Successful exploitation gives an attacker access to session cookies, tokens exposed to JavaScript, page content, and any actions the victim is authorized to perform through the EmbedAI web interface.

Root Cause

The root cause is improper neutralization of user input during web page generation [CWE-79]. EmbedAI does not consistently apply context-aware output encoding when rendering chat message bodies. HTML control characters and script constructs pass through to the DOM as executable markup rather than inert text.

Attack Vector

The attack vector is network-based and requires an authenticated account plus victim interaction. An attacker with a valid EmbedAI account submits a chat message containing a JavaScript payload embedded in HTML tags or event handlers. When another user opens the conversation, the browser executes the script. Because the vulnerability crosses a trust boundary between users, its scope changes and the impact extends beyond the attacker's own session.

No verified proof-of-concept code has been published. Refer to the INCIBE advisory for coordinated details.

// No verified exploit code available.
// Exploitation involves submitting a chat message whose body contains
// HTML or JavaScript that the EmbedAI UI renders without sanitization.

Detection Methods for CVE-2025-0747

Indicators of Compromise

Chat messages in EmbedAI storage containing <script>, onerror=, onload=, javascript:, or base64-encoded script payloads.
Outbound browser requests from EmbedAI users to unfamiliar domains immediately after opening a chat.
Unexpected session token or cookie access patterns originating from the EmbedAI web origin.
New or modified messages authored by accounts that do not normally send HTML-rich content.

Detection Strategies

Query the EmbedAI message store for HTML tags, event-handler attributes, and encoded script markers.
Deploy web application firewall (WAF) rules that inspect chat submission endpoints for XSS payload signatures.
Enable Content Security Policy (CSP) violation reporting on the EmbedAI frontend to catch inline script execution attempts.
Correlate chat viewing events with anomalous outbound HTTP requests from the same user session.

Monitoring Recommendations

Log all chat message create, edit, and read operations with the authenticated user identity attached.
Alert on repeated CSP violations from a single chat resource or author.
Monitor authentication logs for session anomalies following exposure to a suspect message.

How to Mitigate CVE-2025-0747

Immediate Actions Required

Restrict EmbedAI access to trusted authenticated users until a fixed version is deployed.
Audit the existing message database for stored payloads and purge or neutralize any HTML or script content.
Rotate session tokens and credentials for users who may have opened suspect chats.
Track the vendor project for a patched release and apply it as soon as it is published.

Patch Information

At the time of publication, no vendor patch link is listed in the NVD entry or vendor resources. Administrators should monitor the INCIBE Security Notice and the upstream EmbedAI project for a fixed release addressing CVE-2025-0747.

Workarounds

Enforce a strict Content Security Policy that disallows inline scripts and restricts script sources to trusted origins.
Place EmbedAI behind a WAF configured to strip or block HTML tags and event handlers in chat submission fields.
Limit chat account creation to vetted users and require multi-factor authentication to raise the bar for abuse.
Sanitize stored messages at render time using a hardened HTML sanitizer library until an official fix is available.

bash

# Example restrictive Content Security Policy header for the EmbedAI frontend
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'; frame-ancestors 'none'";