On 2011 and earlier Macs with EFI locks:
with the power off, remove a ram module and then turn on the MacBook. Immediately hold Command+Option+P+R to reset the PRAM. Reset the PRAM twice. Then once it chimes, the password should go away. It’s a stupid bypass but it works. After the password goes away, turn off the Mac again and reinsert the ram and reset the PRAM again to include the new ram in the PRAM config.