- http://msdn.microsoft.com/en-us/magazine/cc163744.aspx

Here is what I know about the problem: - Two different Macs (10.8.x, 10.9.x) with 32 GB RAM ran out of system swap due to the size of the Firefox process growing to over 20 GB, and both machines had virtually idle CPUs with no Firefox usage whatsoever - they were unattended - It occurred immediately after upgrading from Firefox 26 to 27.0.1 - The set of pages, tabs, windows was the same before and after upgrading - There does not seem to be a single identifiable URL that causes the problem, but opening a window with this URL and then iconifying it causes memory to be leaked at a substantial rate (at least on one OS X 10.8.5 machine) - http://msdn.microsoft.com/en-us/magazine/cc163744.aspx - I normally have ~25 tabs distributed across ~8 windows, all of which but one are iconified - Memory is consumed at the staggering rate of ~1 GB/hour while the offensive window is iconified - Memory is not leaked per-se - about:memory confirms that heap-unclassified memory is growing rapidly, but as soon as the offending window is opened and no longer iconified, the memory usage immediately drops back to the normal ~1 GB or so - this is also verifiable in Activity Monitor.app, etc - The problem occurs in safe mode, but regardless the only plugins installed are Shockwave Flash, QuickTime, and Java Applet - I have killed Firefox repeatedly and can recreate the same memory usage pattern - I have at least one Mac, however, on which trying to reproduce this does nothing - I've already spent hours trying to determine even the initial cause of this