1274537 - Undo Close Tab should be disabled in private window in Firefox

Status: RESOLVED WONTFIX

(Firefox :: Private Browsing, defect)

Description

[Xiaoyin Liu]

User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:49.0) Gecko/20100101 Firefox/49.0
Build ID: 20160511030221

Steps to reproduce:

1. Open a new Firefox private window
2. Navigate to an arbitrary website in the first tab
3. Open a new tab
4. Close the first tab
5. Right click the title bar. You can click "Undo Close Tab" to reopen the closed tab.


Actual results:

You can reopen closed tab in a private window.


Expected results:

I suggest that Undo Close Tab should be disabled in private window, in order to protect users' privacy if they don't close the private window. Edge, Chrome and Opera all disable "undo close tab" in private browsing mode.

Comment 1

[Josh Matthews [:jdm]]

Given that the knowledge of the closed tabs disappears when the private session is cleared, I don't understand how disabling the feature improves privacy.

Comment 2

[Xiaoyin Liu]

Because users may not close the browser when they finish browsing. If other people see that the private window is not closed, they can just click "undo close tab" to discover what websites the user just viewed, but this trick doesn't work on Edge, Chrome or Opera.

Comment 3

[Justin Dolske [:Dolske]]

I don't think this should be changed -- the undo is quite useful in private browsing mode, just as it is in normal browsing mode.

Further, PB mode's purpose / threat model is only about not storing persistent data on the local machine (ie, on disk), such that exiting PB mode leaves no traces. It's not for protection against someone walking up to a computer with a window left open.

Also note that getting rid of Undo Close Tab would not help, due to other data kept for the life of the window. For example, if you log into GMail, close the tab (but not the PB window), you'll still be logged in if you open GMail in a new tab. The window needs to be closed to prevent this and other issues.

This should be wontfix.

Comment 4

[Josh Matthews [:jdm]]

I agree with comment 3. Thank you for taking the time to share your concerns, Xiaoyin Liu!