Gradio’s _redirect_to_target function accepted an unvalidated target_url query parameter in its OAuth flow, creating a CWE‑601 open‑redirect weakness that allows a user who visits the /logout or /login/callback endpoint to be redirected to any external site. This exposure can be used for phishing, credential‑stealing, or other social‑engineering attacks.

Gradio, the open‑source Python package for quick prototyping, is vulnerable in all releases prior to version 6.6.0 that enable OAuth, such as Hugging Face Spaces using gr.LoginButton. Versions 6.6.0 and later include a fix that strips any scheme or host from the target URL, leaving only its path, query, and fragment.

The CVSS score of 4.3 indicates a low overall severity, and the EPSS score is below 1 %, suggesting a low probability of exploitation. The vulnerability exists on the public endpoints of Gradio apps; an attacker can simply embed a malicious redirect in a link to the /logout or /login/callback endpoint, driving unsuspecting users to a crafted URL. Since the issue is not listed in KEV, there have been no confirmed wide‑scale exploits at this point.