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 https://example.com
3. Enter this in the console:

y = document.createElement(\"iframe\");
y.height = 1024;
y.width = \"100%\";
y.src=\"chrome-extension://hdokiejnpimakedhajhdlcegeplioahd/popupfilltab.html\";
// or y.src=\"moz-extension://...\";
// or y.src=\"ms-browser-extension://...\";
document.body.appendChild(y);  


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.





Found by: taviso@google.com