Other than visiting this forum, is there a mechanism for informing users of security-related updates? Is there a mailing list that we can subscribe to, an RSS feed, or some other active mechanism for informing people who are using the software that a new version has been created and needs to be installed for security reasons? Sorry if this question has been asked, but I've looked through the site and can't find anything related to this topic.
I am not sure about 1.4.x but the upcoming 1.5.x version has a coppermine-gallery.net news feed and a version checker.
You can subscribe to the notifications on sf.net.
You can subscribe to notifications on the announcement board.
As MrTheme suggested, there will be more options for you in the upcoming cpg1.5.x