A scammer will ask to chat with you on another media platform (ex. Discord), saying that they know how to generate free items for you. At some point, they'll ask you to download an extension (cookie manager). One said extension is called EditThisCookie.
Once you download it thinking that it's harmless and helpful, the scammer will ask you to give them your Session ID. Once you give them your Session ID, they will be able to log into your account, this doesn't mean that they will grab a hold of your info, such as: passwords, emails, etc.
How to avoid this hack
Do not download anything that anyone tells you to, and do not give anyone technical information. If someone asks you to download something or give information, they are trying to hack into your account.
If you feel that someone may use your Session ID to hack you, just log back in. Your Session ID resets every time you log in, so the person who you gave your Session ID to will not be able to log into your account.