The issue raised in M-01 was that an operator for a blacklisted user could still approve a token even though the owner is blacklisted. To fix this issue, approve adds the notBlacklisted(ownerOf(tokenId)) modifier which causes the function to revert if the owner of the token is blacklisted.
The issue raised in M-01 was that an operator for a blacklisted user could still approve a token even though the owner is blacklisted. To fix this issue, approve adds the notBlacklisted(ownerOf(tokenId)) modifier which causes the function to revert if the owner of the token is blacklisted.