Single sign-on (SSO) services are supposed to make computing more secure than juggling multiple passwords, but security researchers have proven that LastPass contained design flaws and other issues that could have exposed user credentials to all kinds of exploits.

In a blog post published in conjunction with their presentation at the Black Hat Europe conference, Salesforce security engineers Martin Vigo and Alberto Garcia Illera outlined ways to get around LastPass from outside or internally via the client or server. This included bypassing the service’s two-factor authentication via a locally stored token that’s written in plaintext, fooling the password recovery feature and targeting session cookies, among other approaches. Perhaps most troubling was their discovery of a custom_js parameter cybercriminals could use to inject JavaScript to steal user logins and passwords.

As one might expect, the researchers duly reported their findings to LastPass, which immediately made changes to address the holes. However, as noted by David Bisson on security consultant Graham Cluley’s blog, there are probably holes within many other password managers and SSO services. However, that doesn’t mean it’s better not to use them or to fall back on easy-to-decipher or default passwords, which is often still the case with many computer users.

In fact, Tom’s Guide suggested that it would be difficult for cybercriminals to break into LastPass the way the researchers did if they weren’t also able to get at the user’s server and/or actual machine. As a result, the effort required to break into a server or steal user credentials would probably means hackers pursue other methods instead. Still, given that the service is used by thousands of organizations, the researchers’ findings could have some CISOs and their teams worried.

One of the complicating factors in this case, as SecurityWeek pointed out, is that LastPass suffered a data breach earlier this year; it was acquired in October by LogMeIn, which was also attacked by cybercriminals last year.

This marks the second year in a row the Salesforce researchers identified problems with LastPass. Add them up, and all those things mean the combined organization will have to work harder than ever to demonstrate to customers that they shouldn’t migrate and their information will remain secure.