A flaw was found in WildFly Elytron versions before 1.6.7.Final, in 1.7.0.x, in 1.8.0.x, in 1.9.x, in 1.10.x before 1.10.7.Final, 1.11.x before 1.11.4.Final, in 2.0.0.x before 2.0.0.Alpha7. When using WildFly Elytron FORM authentication with a session ID in the URL, an attacker could perform a session fixation attack. The highest threat from this vulnerability is to data confidentiality and integrity as well as system availability.
CWE-384 - Session Fixation
Authenticating a user, or otherwise establishing a new user session, without invalidating any existing session identifier gives an attacker the opportunity to steal authenticated sessions.