Is the new window related to sites you normally visit or is it unrelated advertising, malware, or some other unwanted content?

In past threads, there was a program for Windows that would create a scheduled task to open a URL in the default browser at certain intervals. The tell-tale sign that it was externally generated was that it occurred even when Firefox had been closed -- the system level request caused Firefox to launch.

no - the new window is always the same - my home page (google.com).

new windows only propagate when firefox is running.

You posted with a Linux user agent. On Linux such issues can probably only be caused by other software that tries to open a new tab/window in the default browser, so you could try to set another browser as the default browser to see if that makes a difference.

I used to use chrome, but switched to firefox for a variety of reasons. i'd rather not install chrome on this clean install if there is a way to determine what is making the system call to open firefox. i'm confortable with the command line, but have never needed to do any system call forensics. is there a way to run a command to see what process is making the system call to open firefox?

I don't know how to distinguish between a new window generated by an add-ons vs. an external source.

However, there is a preference for whether URLs sent from an external source should open in a separate new window or in a new tab in the active window. By setting this to new tab, perhaps that will provide some (possibly inconclusive) data on whether the source is external.

(1) In a new tab, type or paste about:config and press Enter. Click the button promising to be careful.

(2) In the filter box, type or paste link.o and pause while the list is filtered.

(3) For completeness, I'm going to describe three preferences, but the one you need to change for this test is the third one (to 3):

(A) browser.link.open_newwindow

3 = divert new window to a new tab (default) 2 = allow link to open a new window 1 = force new window into same tab

(B) browser.link.open_newwindow.restriction - for links in Firefox tabs

0 = apply the setting under (A) to ALL new windows (even script windows) 2 = apply the setting under (A) to normal windows, but NOT to script windows with features (default) 1 = override the setting under (A) and always use new windows

(C) browser.link.open_newwindow.override.external - for links in other programs

-1 = apply the setting under (A) to external links (default) 3 = open external links in a new tab in the last active window 2 = open external links in a new window 1 = open external links in the last active tab replacing the current page

small progress - can confirm that a new blank window opens at exactly every 61:00 minutes. happens even if i have just one open blank tab and all add-ons disabled. what could be triggering this every 61:00 minutes?

hello,

just check command strace ,it does list out the process and its footprint in detail. Is that any good..

solved: a new window opening every 61 minutes was due to a package: profile-sync-daemon, I reverted back to the older version (5.75) and all is well now.