Mozilla which introduced New Tab Page in Firefox 13 into the controversies here, NTP shows thumbnails of most visited sites from user browser history, Register reports that their user Chris has been presented with thumbnails from content of secured session on NTP in Firefox 13, these thumbnails showed sensitive information like online and banking webmail sessions with account numbers, balances, subject lines etc..
Mozilla responded to Chris queries and they’ve admitted this behavior is undesirable and promised that they’ll release a patch for this. This is what Mozilla stated
“We are aware of the concern and have a fix that will be released in a future version of Firefox. Mozilla remains resolute in its commitment to privacy and user control. The new tab thumbnail feature within Firefox does not transmit nor store personal information outside the user’s direct control. “
Hide or disable Firefox New Tab Page
Mozilla says that these thumbnails are generated from user’s browsing history and they can be deleted by clearing the browsing history. Users who don’t like this feature can switch to blank new tab by clicking on square icon in the top right corner of browser, we’ve covered how to permanently disable it.
Use Private Browsing mode when computer is shared or when you’re on Public Computer
Users in more danger when they share their Computer or surf from Public computer from Firefox with NTP feature on, Mozilla suggests users to use Private Browsing Mode in such cases.
After all Mozilla added NTP feature with thumbnails by following Chrome and Opera, AFAIK these browser’s have not faced this problem. We recommend users to clear browsing history on daily basis using tools like CCleaner to avoid these situations.
Source: The Register