When trying to debug for another user sometimes it is helpful to be able to log in as that user. In the past magic was done by admins by storing the encrypted passwords, setting to a new temporary password, logging in, and then resetting the old encrypted password back.
Luckily modern Oracle versions we have the concept of a Proxy user. This allows connecting as one user but masquerading as another user (once proper permissions have been granted of course).
So far I have done this with SQL Developer and SQLPLUS, instructions are below for a test case.