The riddle went unanswered, and Shlomi submitted it also to members of the review committee, getting only blank stares, including mine.
Who will open your present,
Wanting to give away the pass at all costs, Shlomi then published a new post, including subtle and less subtle hints.
Looking at the hints, it became clear that the object of the riddle, which I could not recognize, was my own MySQL Sandbox. Shame on me for not recognizing it? I don't know. I would never have guessed that a tarball is "your present". Perhaps I have too much a practical mind!
Anyway, thanks Shlomi for this bit of entertainment!