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Langflow - Stored XSS via Malicious SVG Upload

High

Synopsis

The '/api/v1/files/images/{flow_id}/{file_name}' endpoint serves SVG files with the 'image/svg+xml' content type without sanitizing their content.

Since SVG files can contain embedded JavaScript, an attacker can upload a malicious SVG that executes arbitrary JavaScript when viewed by other users, leading to stored cross-site scripting (XSS). This allows stealing authentication tokens stored in cookies, including JWT access and refresh tokens.

Solution

No known solution

Disclosure Timeline

Jan 20, 2026 : Initial contact
Jan 27, 2026 : Second attempt
Feb 04, 2026 : Third attempt
March 23, 2026 : Informed the vendor that, unless we hear back from them, the TRA will be published on Friday, the 27th

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