Steps to reproduce: 1. Load http://www.mozilla.org/. 2. In the same tab, load http://www.homestarrunner.com/sbemail.html. 3. Press Back. Result: About 30% of the time, there's a white box and a black box covering portions of http://www.mozilla.org/ in the same place as the Flash things on the strong bad page. Turning off fastback (setting browser.sessionhistory.max_viewers to 0) makes this problem go away, so this bug might be due to fastback. This bug might have security implications. It at least allows an attacker to cover part of a target site with a white box or a black box. If the boxes can contain more interesting graphics than a single solid color, or if the boxes can be small and plentiful, this bug allows introducing new text onto the target site, such as "bankofamerica.com has moved to bank.evil.com". I am using: * Mac OS X 10.4.2 (latest) * Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b4) Gecko/20050715 Firefox/1.0+ (today's nightly build on Mac) * Flash player 7,0,24,0 (latest).

Related to bug 277067.

Sounds like a serious fastback blocker for Mac.

We need to ensure that we make a "SetWindow" call on the plugin (with the clipo rect set to empty) before displaying the new page. This is similar to the issue that bug 277067 is about. Do we really need the security flag on this bug?

Neither Simon or myself have been able to reproduce this... can you provide any more details that might help?

WFM in Aug 3 builds and later. july 15 bug july 26 bug aug 1 bug aug 2 bug aug 3 no bug aug 4 no bug aug 6 no bug I'm curious whether other people see this bug in older builds (on Mac), and what change fixed it.

Marking WFM, feel free to investigate the fix details further though.