Is this on stable or experimental?

Im not sure what you mean. you mean stable or experimental servers?

I play on the Fragnet.net servers

I am new to this game, so explanations would be appreciated.

Hi,
in 0.37.115791 the Zombies are far more dangerous and you start to bleed so often that rags are one of the basic things. My experience is that they stopped attacking the head. Nearly every time I found and wear some ballistic helmet (BTW: Nice to find blue ones and the possibility to spraypaint them) but started to bleed 2 of 3 times after an attack.
I love this change, because I guess it will make the game harder and more people are forced to shoot for zombies.

There's two versions of the game that you are able to access.

The first is known as 'stable' and is the build that the majority of players will play. The current stable version is 0.35.115188.

Experimental is an opt-in version that is pretty much a beta test of the next stable release. It will say DayZ [experimental] in your Steam library, and the current version is 0.37.115791.

You can check the version number of your DayZ by looking in the top right corner of the game's main menu.

The sever used the 0.35.115188 version

That changelog is for experimental. The problem should be fixed when the experimental build gets pushed to stable.