Open WebUI has Stored Cross-Site Scripting In Profile Picture

Summary

The profile_image_url field on the user profile update form accepted arbitrary data: URI values without MIME-type validation. Two distinct attack paths were independently demonstrated by separate reporters:

1. data:text/html;base64,... in a new browser tab (raresvis, 2025-04-17) — when a victim right-clicks a user's profile picture and chooses "Open image in new tab", the browser navigates to the data: URL and executes embedded scripts in the data: origin. Limited to social-engineering / redirect attacks because the script does not run in the application origin.

2. data:image/svg+xml;base64,... re-served by the application origin (Gh05t666nero, 2026-01-09) — GET /api/v1/users/{user_id}/profile/image decoded the base64 and returned StreamingResponse(media_type=<user-controlled>) extracted from the data: header. With media_type=image/svg+xml and Content-Disposition: inline, the SVG-embedded scripts executed in the application origin, enabling JWT theft from localStorage and full account takeover of any user — including admins — who loaded the malicious profile image URL.

Both attack paths share the same root cause (lack of MIME-type validation on profile_image_url) and are closed by the same fix.

Vulnerable code (v0.7.0)

backend/open_webui/routers/users.py get_user_profile_image_by_id():

elif user.profile_image_url.startswith("data:image"):
    header, base64_data = user.profile_image_url.split(",", 1)
    image_data = base64.b64decode(base64_data)
    image_buffer = io.BytesIO(image_data)
    media_type = header.split(";")[0].lstrip("data:")  # user-controlled
    return StreamingResponse(
        image_buffer,
        media_type=media_type,
        headers={"Content-Disposition": "inline"},
    )