Possible Hack on my gallery

[RootDogg]

I am about to upgrade the gallery as i didn't know it was out of date as i don't admin it much as only a very small community view it every so often (6-7 people) but lately i have been told every so often when looking though a gallery and clicking on an image you get a pop up...

This pop up redirects you to a host of sites includeing domain5.com and other place holder sites. most of which don't work..

My questions are..

Is there a way to find out if a file is in the dir and shouldn't be?
Is there a how to on making your gallery secure (things to check)?

Any is there any advice anyone wants to give me on how to fix this..

feel free to call me a noob or what not

Cheers for the help in advance!

[Nibbler]

Sounds like you installed this plugin - http://coppermine-gallery.com/forum/index.php?topic=31166.0