According to a recent email from TrendLabs Security:
In this month's patch Tuesday, Microsoft addressed the recently discovered zero-day vulnerability in Internet Explorer that also emerged from the Hacking Team leak. The said vulnerability, covered in MS15-065 and rated as 'critical', could allow attackers to take control of the system once successfully exploited. In addition, a proof-of-concept (PoC) code has been spotted by (TrendLabs Security) threats researchers. Microsoft released a total of 14 security bulletins, 4 of which are tagged as 'critical' and the rest as 'important'.
There were also critical vulnerabilities announced by Oracle and Adobe.
Ubuntu users were relatively unconcerned (provide they downloaded the latest patches for the Adobe flash viewer).