A group of researchers at University of California, Berkeley has called into question the security of password managers, particularly those that are browser-based.
In an analysis of five web-based password managers the researchers found "critical vulnerabilities", with four found to allow hackers to steal credentials from a user's account.
They said: "Our study suggests that it remains to be a challenge for the password managers to be secure."
Dangers highlighted included cross-site scripting attacks abusing cookies, phishing attacks, and possible confusion between authorisation and authentication.
The researchers were also concerned that bookmarklets used to identify sites with saved passwords could lead to theft of login details.
They explained: "Widespread adoption of insecure password managers could make things worse: adding a new, untested single point of failure to the web authentication ecosystem.
"After all, a vulnerability in a password manager could allow an attacker to steal all passwords for a user in a single swoop."
Password managers LastPass, RoboForm, My1login and PasswordBox all responded when contacted, fixing all the bugs except those associated with linking multiple accounts belonging to the same user, according to the researchers.
The remaining password manager could not be contacted at the time of writing.