Hello All
First of all my apologies, the title of the post is slightly miss-leading but its just to get the attention (a trick I learned recently :)) but its also true.
Everything that you have opened on your system i.e. in File Explorer (nautilus, Caja) or in your browser (Mozila Firefox or chrome etc), every file, every image, every video, a thumbnail is created for it in /home/<user>/.cache/thumbnails.
This folder is there to cache all the thumbnails so that time can be saved but not creating them again and again just like the thumbs.db in Windows but the problem is that it creates thumbnail of everything, from the beginning of installation to this point. Say if an attacker gain access to your system, He/She can copy this folder and can get a glimpse of what you were up-to.
Along with the privacy disadvantage, this folder also takes up alot of space as well especially if you have years old installation, Kindly have a look now and see what is stored on yours. This folder can be safely deleted
Waqar Afridi's Blog 