Bitcoin Forum

Hello,
I have seen a seller selling hacked accounts for really low on forum.
Can I know is it possible to hack that many accounts without knowing password or emails? Is there any loophole on forum????

The forum's database was leaked in 2015, the databasedump contained the hashed passwords of all users at that time.
Since the databasedump has been on sale on a couple of darknet marketplaces, some people started bruteforcing the user's passwords obtained from the database leak. So, if you have an account older than 2016, it was/is a good idear to change your password, cause sooner or later, one of the databasedump's buyers will probably be able to bruteforce your password.

Other sources might be successfull phising attempts and the fact that a lot of people re-use their passwords.

As for your last question: AFAIK, there is no current loophole in the forum. Only one or two people are able to access the database, that's about it.

How do you know they're hacked? Do they openly state so? And as above, people will have only got their accounts hacked if they had weak passwords and didn't change them after the forum hack.

There is no such known loophole on the forum.The users claiming to be selling hacked accounts either from the database breach back in the day or the ones with common passwords.Even if the account is hacked and you buy it,someday the original owner would be able to prove the ownership making the account worthless.
If you see someone hacked accounts,you should negative trust them or message their threads to DT members.