LastPass Extensions for Chrome & Opera Can Leak Passwords

Tavis Ormandy (who works for Google's Project Zero) has been following LastPass, the password manager, for years. In 2016, he found problems with their extension for the Firefox browser that could allow a remote code execution. He has also found password theft vulnerabilities in the past. They got patched.

Ormandy's latest escapade involves his discovery of another password-stealing potential vulnerability. LastPass says this one got fixed and auto-patched, so users have no worries. More on that later.

On the Project Zero blog, he revealed how the password manager could be tricked into showing the password of the most recently visited site when the Chrome or Opera extension was being used.

Of course, he tweeted about it. "LastPass could leak the last used credentials due to a cache not being updated," he said. "This was because you can bypass the tab credential cache being populated by including the login form in an unexpected way!"

Well yeah, but what happens as you go down that unexpected path? When running those extensions, let's say you go from one site to another. If the second site is malicious, it can force Chrome to access the password that was used on the first site. As Ormandy put it, "That means via some clickjacking, you can leak the credentials for the previous site logged in for the current tab."

There seem to be other problems in the extensions. The generation of arbitrary hotkey events was possible since one routine didn't check that the event which was being processed was trusted. Since the keys can be arbitrary, they could be malicious in content.

Additionally, some security checks could be disabled by putting the string "https://login[dot]streetscape[dot]com" in code.

Ormandy also found that a crossdomaincheck routine would bypass security checks.

LastPass issued their own retort for all of this flare-up.

They said that "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."

Version 4.33.0 is the patched version of LastPass, so a check if the autoupdate happened is possible.

Pay no attention to the man behind that curtain. Move along, now.

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.