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I frequently switch between Chrome and Firefox and so I often mistakenly hit Ctrl+Shift+N to open a private tab in Firefox and instead it performs the Undo Close Window function to open or restore the last closed window.

Often times I'm surprised at the window that comes up. For example, today I hit Ctrl+Shift+N in Firefox and I see a pdf banking statement come up from a secure major U.S. banking site I logged out of yesterday.

If I copy and paste the url for this window into a new Firefox tab then the site requires a login.

How is this happening? Is this a security hole? And is there some way to disable this feature?

User
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3 Answers3

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Firefox caches web pages and other content you've accessed recently so it doesn't have to re-retrieve it when you do something like close and reopen a tab. It isn't really a security issue because you accessed the URL previously. If you clicked reload you would likely get the login page.

This is one of the reasons most banks suggest you close your browser window on their logout page.

You can disable the cache in Firefox but browsing will get noticeably slower. You could also browse to sites you don't want cached in a Private Browsing window and the cache will be cleared when closing that.

Patches
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Three solutions here, whenever you are finished with confidential websites (e.g. banking) you could always:

Option 1

  1. Signout on a seperate tab from the one that you were actively using.
  2. Ctrl + N
  3. Switch back to the banking tab (the actively used one). Alt + Tab might work (depending on the OS)
  4. Ctrl + Shift + R
  5. Ctrl + Shift + W
  6. Ctrl + Shift + N
  7. The webpage should now appear as the login screen (effectively locking the unwanted person out).

Option 2

You could just simply use the TOR browser (an ultra-secure Firefox-based alternative) for banking (or other secure sites), it may not work with all websites and will be very slow, but we're going for security here, right? Using a VPN will also increase your security, then once you close the TOR browser it will wipe everything you had open/saved!! You should be cautious while using the TOR browser while it may lead to inaccurately accused crimes or other charges. (Read the Tor browser link for more information)

Option 3

Literally, just open your banking/confidential websites in a secure/private session (like what Patches said)
See Firefox Private Windows

255.tar.xz
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I figured out a way to reassign Ctrl+Shift+N to New Private Window using the ShortKeys add-on. I cross-posted the following from another similar question I just answered.

This add-on solves this problem in 90% of scenarios:

It allows you to create your own custom keyboard shortcuts -- and among those, you can finally invoke a blank New Private Window pressing Ctrl+Shift+N. It is able to override Firefox's own powerful Undo Close Window (a command which raised the question author's eyebrows, and still remains available just a right-click away) -- and finally makes this combo work just like it does for New Incognito Window in Chrome/Edge/Chromium-based browsers and also similar to its equivalent in Apple Safari. enter image description here

Limitations: THE NEW SHORTCUT ONLY WORKS IF YOU ALREADY HAVE AN ACTUAL WEBPAGE LOADED. Due to Mozilla Firefox's own "security" measures, it does NOT work on any of the "about:" or internal pages (about:blank, about:newtab, etc.), as well as on a new tab, empty windows, downloads/bookmarks manager, pop-up, etc.; as I type this, I also realized it does not work if the cursor is in an active text input field -- I have to click the empty blank area of this webpage first, and only then Ctrl+Shift+N will work.

Another limitation: I'm using Firefox on Windows, and I tried assigning Mac-inspired shortcuts such as Ctrl+, (comma) and Ctrl+. (period) to Open Settings Page and Open Extensions Page respectively. No idea why, but that didn't work, sigh (I was able to create these and more for Chrome/Edge for Windows with the extension Keyboard Shortcuts though, for anyone interested).

Lucas Pestana
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