jquery double counts my checkboxes

I'm trying to get all of the checked checkboxes on my page using jquery, but it appears that jquery is counting boxes with the checked="checked" attribute as well as boxes that actually appear to be checked.

I am using the following code to retrieve the checked boxes: $("input:checkbox[name='repo_filter']:checked");

With the checkboxes getting generated like this:
<input type="checkbox" name="repo_filter" checked="checked">

It returns that there is a checkbox checked if the box originally had the checked attribute even if it was since unchecked.

Any help is much appreciated.