Site search results include hidden content

Hi,

I've got a simple config - anonymous users, through TAC Lite, have no permissions to access forums (there are many more fine-tuned permissions too, which is why I need TAC Lite in the first place, but for the sake of this issue, this simple one illustrates it). This works fine if a guest tries to access any of the forum listing pages - no topics are displayed. However, going directly to a post URL displays that post. Also, even worse, site search (core) displays relevant forum posts on the results page.

Any ideas would be greatly appreciated. I've tried searching the issue queue but to no avail.

Thanks in advance.