Linux security in action?

I know that this is pretty trivial, but thought I'd mention it all the same.

I downloaded the binary installer for Poseidon 4.2 and attempted to run it by opening a bash shell and retrieving the file using the shell's auto-complete feature. But the shell couldn't locate the file for some reason. Then it struck me: if you are trying to execute a file, the shell will not bring it up unless the file has its execute bit set, which, in this case, wasn't so, in order to prevent malicious programs (especially those downloaded from the Internet) from executing. Neat.

Or is it Firefox which sets the file permissions during the download?