MacBook Pro early 2011 13-inch *Firmware password*
bought a MacBook pro yesterday and the buyer didn't know anything about mac he wanted to erase data on his HDD, he read this article and did, but the mac stuck on recovery page (actually he create an OSX Base System on whole of HDD) and his couldn't fix it and sold it. I tried to fix it, but I realized it has firmware password when I hold ALT key, and any command has disable lick reset Nvram, COMMAND+R and ... it just goes to recovery page automatically.
I texted him and asked about password and iCloud, he said I never set a password on it, he doesn't know anything about firmware password! and said I checked it in my iCloud, and it is removed! He said my default password on my MacBook was abc123 and I used it for all the time. Also said for wipe my HDD I did whatever was advised in that article link I sent you.
it's weird how it possible? Does anyone have any idea? Thanks.