Firefox Private Browsing Mode Bypassed By Add-Ons
One of the greatest strengths of the Firefox web browser is the Mozilla development community that has produced thousands of add-ons to improve the browser or the browsing experience in the past.
Update: Mozilla fixed the issue in the meantime.
Mozilla introduced private browsing recently in Firefox. Private browsing mode prevents the permanent storage of the browsing history, cookies and other information.
While Firefox itself prevents local data from being remembered after private browsing sessions, add-ons until now have not necessarily as there was no requirement for add-ons to respect the private browsing mode of the browser.
This means that data may still be saved on the local system while in private browsing mode if add-ons are installed that ignore the mode.
That's obviously not the intention of private browsing mode, and Mozilla has addressed the issue in a new blog post linked here.
Mozilla explains that private browsing mode has been designed to prevent that browsing data such as the browsing history is stored on the local computer. Browsing data refers to data that can be used to identify the websites the user was on. This includes website addresses, cookies or temporary data.
Mozilla outlines how it wants to go forward with the mode in regards to browser add-ons:
- If your add-on stores browsing data in any way, it must support PBM. This support cannot be disabled in any way, not even with hidden preferences.
- If your add-on stores some other type of personal data, support for PBM is optional. What we did with Fire.fm is a good guideline: have a preference â€œsupport PBM for the data this add-on handlesâ€, turned on by default.
Mozilla will enforce this new rule starting at the end of March 2010. Add-ons that are updated or newly added to the Firefox add-on repository after that date will be rejected if they do not comply with the new privacy rules. The rules will however have no effect on add-ons already listed on the extension gallery.
This means, at least in theory, that you may run add-ons right now that are not in compliance with the new rule set. Also, after March, you may still download add-ons that are not in compliance if they have not been updated in the meantime.
This is for instance the case for old add-ons that have not been updated in a while.Advertisement