Hi Jeno, These go through "To send work to the shark: email your query letter to janet at fineprintlit dot com"
Ms Janet Reid is a wonderful agent and Fineprint Lit is a well known agency. Note that she's posted nine deals in the last twelve months and most are women's fic or Fic-Suspense/Thriller and a few non-fic, but I think a good agent would be able to crit a query no matter what the genre.
Yes, I suppose someone could steal your idea if it is posted, but odds they'd get something out to agents before you do would seem unlikely. Truthfully, just reading her past query edits would be invaluable, maybe as much as having your query looked at!
Meg