This first started to appear on the Dark Souls subreddit, and players who use BitDefender or Windows Defender have started complaining that their save files have been corrupted. These anti-virus software could damage the save files, making you start all over again...not something you want to do in Dark Souls.
So the solution is to exclude the game from your Anti-Virus software, however, BitDefender is aware of the problem, and got in touch with PC Gamer. They say...
"We found out that the Dark Souls caches (saved progress in the game) are not altered, but the process that tries to access them is being blocked from saving or loading because it is not signed by a trusted certificate. The Bitdefender anti-ransomware feature Safe Files protects different user files from being altered by applications that are not considered legitimate."
Right now, the best you can do is to add the executable of the game to allowed applications in the Application Access area, and bak up your save file.//TODO: Rijesiti rating i odkomentarisati ovo kad rijesim ?>