Mozilla published a new version of its Firefox web browser on Tuesday that fixes five security vulnerabilities, two of which it rates as critical.

Firefox version 3.0.2 fixes a memory corruption bug and a separate critical bug involving privilege escalation and the XPCnativeWrapper component of the browser. Both create possible mechanisms for hackers to inject hostile code into vulnerable systems using rigged websites, or perform similar tricks.

The same two critical bugs are fixed in Firefox 2.0.0.17, for those still using the earlier version of the browser. There’s no evidence that either critical flaw has been exploited by hackers but prudence would steer towards early patching. Judging from past experience automatic updates from Mozilla will appear in about a day or so.

Mobile phone company Sony Ericsson announced Tuesday that it will launch a new music service called PlayNow Plus, which will feature unlimited music downloads.

As first reported by CNET News, the new service will be powered by British music-download firm Omnifone, and will feature music from all four of the largest recording labels, the company said in a press release.

PlayNow Plus will compete with Comes with Music, the music service launched by Sony Ericsson rival Nokia earlier this year. And out of the gate, PlayNow can offer a more complete music library than Nokia’s offering. EMI has yet to join Comes with Music.

But Sony Ericsson may not give away as much music as Nokia. According to the press release, Sony Ericsson will eventually offer users 5 million songs, which will be wrapped in digital rights management software, and keep them for the length of their contract. After their contract ends, the company will allow them to keep “a number” of DRM-free songs.

According to a report from Dow Jones, Martin Blomkvist, Sony Ericsson’s manager of content acquisition said PlayNow Plus users can keep 100 DRM-free songs for each six months of their PlayNow contract. In comparison, Nokia allows users to download as much music as they want for the 12 months and keep those songs forever. The music is indeed swaddled in copy-protection schemes.

Why would people want to buy DRM infected music when they can have a DRM free one I don’t know.

Yahoo Messenger 9.0 became available on Tuesday–a week after Yahoo’s target launch date and interestingly, a week after Microsoft released its beta update of Windows Live Messenger. Yahoo Messenger 9.0 as dramatic an update of its instant messenger as Windows Live beta is of Windows Live Messenger 8.5, and it introduces some pleasant improvements over version 8.1 that will satisfy Yahoo loyalists. Among them are a redesigned interface with more skins, more space, and the excellent ability to see scaled public images and videos in the chat window.