URL Redirection to Untrusted Site ('Open Redirect')
The Bitly oauth2_proxy in version 2.1 and earlier was affected by an open redirect vulnerability during the start and termination of the 2-legged OAuth flow. This issue was caused by improper input validation and a violation of RFC-6819
CWE-601 - Open Redirect
An open redirect attack employs a URL parameter, HTML refresh tags, or a DOM based location change to exploit the trust of a vulnerable domain to direct the users to a malicious website. The attack could lead to higher severity vulnerabilities such as unauthorized access control, account takeover, XSS, and more.