malicious code being uploaded as avatar images...

Perhaps this is already common knowledge, but I really don't have the time to do a thorough scan of the forums here.  

There have been a number of times now in the last few months where my site was successfully infected.  The infections were injected as avatar images.  

Example:   .../public_html/modules/boonex/avatar/data/images/50155i.jpg

Does anyone know anything about this and how it can be prevented?

I am on the forums daily. And this is news to me.

How did you detect that this was how it was being done, and do you have a name for this infection?

not even possible to use any injection as a jpg or other photo formats

As far as I know... this code (in avatar module)

    var $_aAllowedExt = array (

        'jpg',

        'gif',

        'png',

    );

will block malicious code.

Yea, i also believe it is not possible, but i figured i would ask about the method of detection and a name of infection.

Are you running 7.0.9?   There were some exploits  in previous versions that were fixed.

Ya, I'm running 7.0.9

When I asked my hosting company what kind of infection it was, they replied:

The maldet scan report normally states what type of infection was found in the file but looking back at it does not. It just stated the name of the files that it flagged as malicious.

The files were...

FILE HIT LIST:
: /home/mysite/public_html/modules/boonex/avatar/data/images/50155i.jpg
: /home/mysite/public_html/modules/boonex/avatar/data/images/75931.jpg

Do you still have copies of the images in question?  Many of the PC virus protection SW companies will analyze files for viral content.  I've heard of jpgs harboring viruses in the past, but I thought that era was long over.  I'm also pretty sure resizing images server side, would destroy any such viruses.  Since one of your image urls is a resized image, I find it really hard to believe any type of malicious code could have survived.  It's more likely some sort of false positive.