According to security company Secunia, Apple is now the company with more security vulnerabilities, taking over Oracle, which falls to the second position. On the third position is Microsoft.
This doesn't mean that Mac OS X is the most insecure operating system, since Secunia's report doesn't take into account the nature of the security problems. Most of the security problems are in applications and not in the operating system itself. [Ars Technica]