Hi Peter,
Oh, wow, thank you! Wordfence had alerted me to the possible malicious code in that file but the option was only to delete the file and then my entire site broke so I thought it was a false positive. I should have looked into that further, I guess. I hadn’t had any other problems so I didn’t worry about it.
As a quick check, I removed the code and the site seems to be working and, so far, the code hasn’t been put back. But, I will change all passwords and read through all the documents you sent.
Thank you so much!