Spring Security OAuth, versions 2.3 prior to 2.3.5, and 2.2 prior to 2.2.4, and 2.1 prior to 2.1.4, and 2.0 prior to 2.0.17, and older unsupported versions could be susceptible to an open redirector attack that can leak an authorization code. A malicious user or attacker can craft a request to the authorization endpoint using the authorization code grant type, and specify a manipulated redirection URI via the "redirect_uri" parameter. This can cause the authorization server to redirect the resource owner user-agent to a URI under the control of the attacker with the leaked authorization code.

References:

https://pivotal.io/security/cve-2019-3778