I have a spreadsheet with lots of private data. It is stored in an encrypted drive but for added security, have been saving it with a password (data format xlsx) Recently, the file was flagged for recovery by Libreoffice probably because I shutdown without saving it. Anyway, the recovery process worked and saved the file but the password protection was lost. I would consider this a security bug, maybe even a CVE. Running on Debian testing (Buster) which is version 1:6.0.2-1 Sorry not going to attach the file (for obvious reasons) but trust that developers can reproduce it.
*** This bug has been marked as a duplicate of bug 93389 ***