Recently I have seen there has been a LOT of steam scams going around where anyone you have added can message you about a free steam gift card you can activate or something along those lines. Make sure to read the link as it will say something like "stemcomunnitily" or "steamcommunite". These scams will hijack your account so I suggest you all stay away. If you are unlucky enough to be scammed, make sure you have anything that can prove the account is yours, steam card codes, credit cards, debit cards etc. Also make sure 2FA is enabled and make sure to change password IMMEDIATELY if this happens.
Example of scam (obviously dont copy link and go on it. You can see they spelled community wrong):
Stay safe everyone.