I tracked down a snippet of Jen's warning about the Uni Gottingen cloud variables from this message. Whether or not the original post is deleted or simply private, I don't know, but I'm guessing it was taken down to prevent people from getting any ideas about using these blocks, which might explain why I remember fsul having posted here about the cloud variables they created, and why I can't seem to find that post anymore.
And as for, "malicious scripts that abuse JavaScript to cause havoc on browsers," that was referring to a script that would crash your browser if you attempted to See Inside (this was to prevent people from modifying the cloud variables in an undesirable manner). So not only are the Uni Gottingen cloud blocks a no-go, but so is that crash snap block.