Hang on a sec, every OS has unfixed security issues at ay one time, either because they've been found very recently or because of other developmental reasons. So assuming there is a widely used OS out there (I'm including Linux but excluding niche OSs like ZOS) without a current security vulnerability is ludicrous.
On top of that.
Who has the chart, which shows that windows although has had the most number of holes (unsurprising due to it's dominance and there for targeted the most), it actually had the least number of unresolved holes.