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.
Edit 2: I'm using CiviCRM 4.6.37 and Drupal 7.59. And I'm not sure if it was actually CiviRules or clicking something in the API Explorer... I downloaded CiviRules extension first before I played around with API Explorer. My reasoning for poking around API was to see if there was some way to link/unlink user IDs with CiviCRM contacts and reuse a general username/account for changing members. Hopefully that makes sense! :-/
Edit 3: Problem is fixed. IT support at my organization’s end conquered the WSOD. Lesson learned: don’t mess with API if you don’t know what you’re doing. ¯_(ツ)_/¯
Thank you all for your responses!