A potential privacy loophole has been uncovered in the location based social network, Foursquare. The company made much of their improved privacy settings in the wake of Facebook implementing their own location based check in system, but one privacy aspect seems to have slipped through the net.
The problem arises if you have linked your Twitter account to Foursquare but wish to keep your Twitter profile private. In the privacy settings, it is possible to de-select the 'Let everyone see the links to my Twitter profile and Facebook profiles (only if I've connected them below)' option, but regardless of whether it is selected or not, viewing a profile which the user has connected to Twitter will still reveal the user's Twitter account name in the profile url, meaning they can be easily found on the micro-blogging site.
For example, if someone with the Twitter username JohnABCDEFG links their account with Foursquare, but deselects the option to show the link to their Twitter account, their Foursquare profile url would be http://foursquare.com/user/JohnABCDEFG. Obviously this exploit also works in reverse with people being able to find a user's Foursquare account from their Twitter username with ease if the accounts are linked. Hopefully, Foursquare will rectify this problem as soon as possible.
