Dropbox has restored sharing services after patching a flaw that allowed attackers to access shared files under specific conditions.

The simple vulnerability meant the location of the shared files could be disclosed to website administrators via referral headers.

That would only happen if a user clicked a link to the website that was contained in the shared file.

Dropbox disabled sharing for all but business users after the vulnerability was disclosed and patch developed.

"Once the link is clicked, the webmaster of the third-party website can view the incoming link in e.g. web analytics software," staffer Jan Willem Aldershoff wrote.

"The incoming link is the link to the shared file which means it can now also be viewed by the third-party webmaster."

Dropbox was unaware of exploitation of shared files via the bug.

The minor bug is one of several Dropbox has contended with of late. Last month it patched the Heartbleed vulnerability, controversially informing customers via a blog post rather than the more-likely-to-induce-action email.

Last August, Dropbox admitted spammers raided user email addresses contained in a project document after a staffer reused a login password that was subsequently compromised.

The web attic implemented two factor authentication after the breach and unspecified spam catching wares on its infrastructure.

Trend Micro security boffin Rik Ferguson criticised Dropbox at the time for using real customer data in a project document and for sending password reset links over email to customers. ®