After the fix_cache_key.php problem was solved last night, I tried to login as admin to my store.
But then I was surprised that the password that worked for me 7 hours earlier, didn't work anymore.
So I reset the password, which was emailed to me promptly, and used it get login (then immediately change the password, of course).
I could have forgotten all about this incident but since this is an important security issue, for which I have no explanation, I am wondering: What could possibly reset the admin password? (you can safely assume that I didn't forget or mistype it).
I looked at the admin activity log and found no evidence that someone else (e.g. a tech at the web host company as part of troubleshooting) could have changed it.
So, what other possibilities are there for resetting the admin password unbeknown to me?
For example, is there a security feature in Zen Cart that makes the password expire if it's older than X days? (similar to the feature that exists in Windows 2000/XP/Vista)