Skype has suspended its password reset function after reports that the feature could be used to hijack the service's accounts.
The vulnerability, which emerged on a Russian blog about three months ago, could have exposed answerphone messages, old text message conversations and user details including date of birth.
Skype is looking into the problem.
"We have had reports of a new security vulnerability issue," said engineer Leonas Sendrauskas.
"As a precautionary step we have temporarily disabled password reset as we continue to investigate the issue further. We apologise for the inconvenience but user experience and safety is our first priority."
The hack involves using a victim's Skype-registered email address to create a new account which is also linked to an email account owned by the attacker.
If a password change is then requested using the target's username, the hijacker can access the resulting reset token via the Skype app itself using the newly-created bogus log-in.
The security hole was confirmed by The Next Web.
The news comes amid Microsoft's efforts
to convince members of its Windows Live Messenger chat tool to switch to Skype.
After temporarily removing the ability to reset passwords while it worked on a solution, Skype has now issued a fix for the security bug. The company also issued the following statement:
"Early this morning we were notified of user concerns surrounding the security of the password reset feature on our website. This issue affected some users where multiple Skype accounts were registered to the same email address. We suspended the password reset feature temporarily this morning as a precaution and have made updates to the password reset process today so that it is now working properly. We are reaching out to a small number of users who may have been impacted to assist as necessary. Skype is committed to providing a safe and secure communications experience to our users and we apologize for the inconvenience."