.quarantine and .tmb folder

Hi

I just found via FTP two folders on the top of my server. “.quarantine” is empty but “.tmb” has a lot of .png files in it. i’m feared they are from maleware. Google doesnt bring me a solution but i found the Release notes entry on you website

2.6 (24th Oct ,2017).tmb and .quarantine folders hide

waht are these folders for and are they necessary?

Best regards
Alex