i was wondering what data is included in clog, so with short google search i found decrypter script. with fast reading through document i found several privacy and security concerns if anyone manage to get to your clog files.
so what info is in them?
your IP address and its lookup info (country and city from where you are playing), nick (probably gaijin username), original nick, game registration time, token (probably auth token, so this could or could not be an security issue depending on how they handle this on client and server side), username on your computer, your system info, your friends list and their online status.
good news is that clog files are private on CBR (only for authors and employees), so someone getting access to them is unlikely, so be careful not to post your clog files publicly or share them with non authorized persons.
btw i didnt check the clog in detail so there could be more private/security info, but even with what i found so far it is enough to know that you should not share your clog publicly.