I installed an app (a managed package) to my org's Salesforce instance this morning, and shortly thereafter noticed that in FLS, visibility had been removed on dozens of important fields, across multiple objects for all user profiles. This was extremely disruptive, since it broke our API integration when it couldn't fin the fields it was supposed to be updating; I had to go back and reset all of these fields FLS setting to visible one by one to get our system running again.
Why on earth would this happen? The app developer claims he's never heard of this problem before and doesn't even think it's possible for his app to do that. Did I do something wrong when installing the app?
Some additional detail: I had first briefly installed the app to our sandbox, and then later to production. I never deliberately set up any change sets or deployed anything from Sandbox to Production (I just went back to the AppExchange and installed again, this time choosing Production), but when I look at our Deployment Status page it shows a "deployment" at the moment when I installed the app from the app exchange to production. Is that normal?