The fun folks at Kaspersky Labs' Securelist blog have found something nasty in Apple's Safari Browser, which they say lists user IDs and passwords in plaintext.

Detailed here, the problem derives from Safari's retention of browser history as applied in the “Reopen All Windows from Last Session” feature that enables users to quickly revisit the sites they opened during a previous Safari session.

Sadly, however, Kaspersky has found that the document Safari creates to allow such restoration is in plaintext and contains user IDs and passwords. The file is hidden, but isn't hard to find once you know what you are looking for.

As Kaspersky's post helpfully points out, “You can just imagine what would happen if cybercriminals or a malicious program got access to the LastSession.plist file on a system where the user logs in to Facebook, Twitter, LinkedIn or their online bank account.”

We can indeed.

Kaspersky's been kind enough to point out the problem to Apple, and also says it is not aware of any malware targeting the flaw. But the blog post was made last Friday, so perhaps some naughty malware-writers spent the weekend preparing just such a tool.

Apple's Security feed is silent on the matter, but panic seems premature: Kaspersky says the problem only affects OSX10.8.5 running Safari 6.0.5 (8536.30.1) and OSX10.7.5 with Safari 6.0.5 (7536.30.1). ®