USN-5069-2: mod-auth-mellon vulnerability

USN-5069-2: mod-auth-mellon vulnerability

USN-5069-1 fixed a vulnerability in mod-auth-mellon. This update provides
the corresponding updates for Ubuntu 21.04.

Original advisory details:

It was discovered that mod-auth-mellon incorrectly filtered certain URLs.
A remote attacker could possibly use this issue to perform an open redirect
attack.
Source: USN-5069-2: mod-auth-mellon vulnerability