CiviCRM was working fine until I downloaded an extension called CiviRules. I looked into the API for field UFMatch, clicked around in there, and pressed execute (got no warning that it was going to change anything in the database, so I just assumed that it was running a test) and it resulted in no errors supposedly.

I also can't delete the extension, it sends me to an HTTP 500 error. Whenever I input a string search, it gives me a drop menu of contacts with matching strings but when I want to get a list of all the contacts in the database, it takes me to the WSOD!

What can I do to try and fix this?

Edit: it looks like any time I search for something (e.g. contributions, events, participants, contacts etc.), it takes me to the WSOD.