The update says:
“...a hotfix for the vulnerability was released in mid April.
‘As there were no reports of this vulnerability being exploited in the wild, we did not prompt our users to install this update, as there is another update in the pipeline that will be sent out early next week,’ Skype’s Adrian Asher wrote.
He added:
This vulnerability, which they blogged about earlier today, is related to a situation when a malicious contact would send a specifically crafted message that could cause Skype for Mac to crash. Note, this message would have to come from someone already in your Skype Contact List, as Skype’s default privacy settings will not let you receive messages from people that you have not already authorized, hence the term malicious contact.”
Unless I've been stupid and changed that default, I wouldn't put too much store by that - I've had some spam in Skype messenger.