I think Steve has got some good points on why comparing vulnerability numbers is difficult.

I don't think many software vendors would be willing to run the risk of deliberately placing a back door in their software. The benefits compared to the huge risk of disclosure simply aren't worth it.

Apple has done much better at dealing with issues in the past couple years than it did before.

Vendors can take months to create patches, and sometimes users grumble about that, ... But the alternative is to have patches that can be circumvented or aren't appropriate for the vulnerability. It's a difficult balance.

Three of the vulnerabilities can launch malicious code that allows an attacker to snoop on users. The other vulnerability is a DOS attack that will only work in a few cases and crash the media player when it tries to open a file.

We don't have an 'extremely critical' ranking very often. We use the rating sparingly so people will know when the danger is very serious.

An attacker could use the exploit to run any code they want to on a person's system. It could be they want to launch some really nasty code on a user's system.

While the bug in itself could look like a back door, I find it highly unlikely that it actually is a deliberately placed back door.