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I'm relying on Firefox to remember my passwords, using a Master Password of more than 25 characters. How secure is this set-up?

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up vote 23 down vote accepted

In short - Firefox uses triple DES in CBC mode with Master Password.

More details: nice article about this topic is here: and if you want some more details, here is mozillaZine article: This article gives you a detailed comparison between the major browsers.

It is believed that it is safe to store passwords such way, however, I do not trust any software. Maybe it sounds too paranoid, but we can never know where the vulnerability hides.

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One article says to enable FIPS for improved protection. Why isn't FIPS enable by default then? – Roger C S Wernersson Nov 18 '10 at 8:36

In order to answer "How secure are my passwords in the hands of Firefox using a Master Password?" If Firefox has any exploitable bug, then it is not secure no matter how much encryption is wrapped around your passwords. Had the question started with "Assuming Firefox is the most secure browser available in terms of exploits and ignoring any plugins..." then i would agree the answer may be irrelevant. If a click interface that is not susceptible to keystroke logging is used, then the passwords may still be safe even with a keystroke-logger in the browser. If there is a "man-in-the-browser", physically typing in a password can be intercepted and if Mozilla emulates key-presses then these would also be intercepted. If Firefox uses more direct memory access, i still would not be surprised if it could be intercepted.

"Man-in-the-browser" is not a machine level rootkit, but at the application level. Most common is malicious AJAX which can easily listen to every keystroke -- that is AJAX 101. Or could be malicious binary code injected remotely into the browser or into a plugin.

To mitigate "man-in-the-browser", use several different firefox profiles siloed for banking, email accounts, ClipperZ, and others or just use Qubes-OS.

If there is a "man-in-the-machine" or system level rootkit, then all your passwords are owned no matter if they are stored in KeePassX or ClipperZ or Firefox.

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Sounds correct, but irrelevant. This is true even if I don't let Firefox save my passwords. The root-kit problem is true for all applications on the infected computer, not specific to Firefox. – Roger C S Wernersson Jun 28 '11 at 10:30

Firefox sync stores your passwords and transfers them to other synced computers, but doesn't secure them with your master password.

So if an attacker can open your browser and activate sync, then sync with a profile on their browser, your passwords will be synchronised!

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I finally found the time to test this and it seems activating sync requires my master password, if I have one set. This should make your point a non-issue. – Roger C S Wernersson Sep 28 '12 at 17:08

I believe that the password recovery tool from can just bypass this, but I have not checked this specifcally

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I though such tools used a brute-force approach, if protected by a Master Password. – Roger C S Wernersson Nov 22 '10 at 8:42
Nah, usually this crap can just be reverse engineered and the flow of execution modified to skip little requirements like passwords to access local datastores. – atdre Nov 22 '10 at 21:27
Hmm. Define "this crap" please. :-) Also, I believe the password file on Firefox is encrypted – Roger C S Wernersson Jun 28 '11 at 10:31
@RogerWernersson It is, there is an option for FIPS-140 support too ( atdre please gives sources rather than telling lies. – Shadok Oct 10 '13 at 15:01

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