13 million Facebook users have never adjusted their privacy settings on the social networking site.
This is one of the results of a study carried out by marketing blog Marketo, despite concerns surrounding Facebook privacy and the release of Graph Search, the upcoming feature that will allow users to search through posts and pictures.
The study also found that 28% of Facebook users share all or most, of their Facebook posts with groups of users which include more than just their friends.
In addition, 11% say that someone else has tried to access their account without their permission.
The use of Facebook by employers is also highlighted in the study, which claims that a massive 91% of organisations screen prospective employees' Facebook profiles before hiring.
Our advice is to review and adjust your privacy settings as soon as possible, especially with the impending launch of Graph Search. Make sure your pictures and location tags are correctly secured, and remove your own tag from any item you do not wish to have associated with you.