Twitter warns users – Firefox might hold on to private messages
The issue had to do with how long your browser might hang on to local copies of private data such as direct messages, even after they’d actually been posted.
Twitter published an blog article tagged “Privacy” that stated:
We recently learned that the way Mozilla Firefox stores cached data may have resulted in non-public information being inadvertently stored in the browser’s cache. This means that if you accessed Twitter from a shared or public computer via Mozilla Firefox and took actions like downloading your Twitter data archive or sending or receiving media via Direct Message, this information may have been stored in the browser’s cache even after you logged out of Twitter.
We’re guessing that this problem was submitted to Twitter as a bug report, presumably by someone who just happened to look through their Firefox cache files and was surprised to see what showed up there.