lastpass: bypassing do_popupregister() leaks credentials from previous site  
I noticed that you can create a popup without calling do_popupregister() by iframing popupfilltab.html (i.e. via moz-extension, ms-browser-extension, chrome-extension, etc). It's a valid web_accessible_resource.  
Because do_popupregister() is never called, ftd_get_frameparenturl() just uses the last cached value in g_popup_url_by_tabid for the current tab. That means via some clickjacking, you can leak the credentials for the previous site logged in for the current tab.  
I don't consider this a *critical* issue, because I don't think there's a way to control which site you leak credentials from (just the last visited site), but it does seem serious enough to fix.  
To reproduce the issue:  
1. Go to a site you have credentials saved for and click the little \"...\" icon.  
2. Go to  
3. Enter this in the console:  
y = document.createElement(\"iframe\");  
y.height = 1024;  
y.width = \"100%\";  
// or y.src=\"moz-extension://...\";  
// or y.src=\"ms-browser-extension://...\";  
This bug is subject to a 90 day disclosure deadline. After 90 days elapse  
or a patch has been made broadly available (whichever is earlier), the bug  
report will become visible to the public.  
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