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Password-exposing bug purged from LastPass extensions

Still image from the long-running but currently defunct gameshow Password. (credit: ABC Photo Archives / Getty Images)

Developers of the LastPass password manager have patched a vulnerability that made it possible for websites to steal credentials for the last account the user logged into using the Chrome or Opera extension.

The vulnerability was discovered late last month by Google Project Zero researcher Tavis Ormandy, who privately reported it to LastPass. In a write-up that became public on Sunday, Ormandy said the flaw stemmed from the way the extension generated popup windows. In certain situations, websites could produce a popup by creating an HTML iframe that linked to the Lastpass popupfilltab.html window rather than through the expected procedure of calling a function called do_popupregister(). In some cases, this unexpected method caused the popups to open with a password of the most recently visited site.

“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,” Ormandy wrote. “That means via some clickjacking, you can leak the credentials for the previous site logged in for the current tab.”

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