Apple has blocked Java 7 Update 11 (and earlier)
Apple has via their Xprotect anti-malware feature blocked running the Java browser plug-in if it is version 7 Update 11 (or older) due to it being 'insecure'. Unfortunately like what happened on Thursday January 10th 2013 when Apple blocked Java 7 Update 10 (or earlier) Oracle have as of yet not issued a newer 'fixed' version. Last time it was not until Monday 14th Jan that Oracle issued a fixed version so we could be waiting until February 4th if Oracle take as long again.