I don't know if anybody already talked about this, but yesterday, while i was working on a thing, i saw an interesting thing on the wiki. what i read was absurd.
GameOS is allowed to write in the metldr flash region. this is stupid.
Anyone with a little of knowledge would never allowed it, since if you damage that region, you will brick permanently the PS3; this thing should be allowed also on 3.56+ Firmwares.
I always thought that Sony would be not so stupid, but, seems that i'm wrong.
Now, i will not explain how to do that and i hope that no one will ever build a malware to brick your Playstation.
What i suggest is download Homebrews and ANY other executables from well known website, just to avoid this.
DO NOT ASK ME HOW TO DO THAT BECAUSE I WILL NOT SAY IT.