LastPass fixes bug that exposed passwords

The browser extensions for password management tool LastPass suffered from a vulnerability that meant users' passwords could be leaked, a Google Project Zero researcher reported.

Affecting the Chrome and Opera extensions, the vulnerability meant that malicious websites could trick LastPass into exposing usernames and passwords. LastPass explains that the problem stemmed from a "limited set of circumstances" that allowed for clickjacking. The good news is that the security flaw has been patched.

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The even better news is that there is nothing users need to do to protect themselves. LastPass has pushed out an update to the extension that will be automatically installed -- so, assuming you're connected to the internet, everything will be taken care of for you.

In a post on the LastPass website, the company explains:

Our team recently investigated and resolved a bug affecting certain LastPass extensions. Tavis Ormandy, a security researcher from Google’s Project Zero, responsibly disclosed the issue to us. His report revealed a limited set of circumstances on specific browser extensions that could potentially allow an attacker to create a clickjacking scenario.

To exploit this bug, a series of actions would need to be taken by a LastPass user including filling a password with the LastPass icon, then visiting a compromised or malicious site and finally being tricked into clicking on the page several times. This exploit may result in the last site credentials filled by LastPass to be exposed. We quickly worked to develop a fix and verified the solution was comprehensive with Tavis.

We have now resolved this bug; no user action is required and your LastPass browser extension will update automatically.

Additionally, while any potential exposure due to the bug was limited to specific browsers (Chrome and Opera), as a precaution, we've deployed the update to all browsers.

Under the code of responsible disclosure, details of the flaw were only made public on Sunday. Researcher Tavis Ormandy's finding were revealed on the Project Zero website.

He explains:

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.

The vulnerability meant that a specially coded malicious site might be able to access the credentials used on the previously accessed site.

Just make sure that you're updated to LastPass 4.33.0 or later, and you will be safe.

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