As long as you use SteemConnect to sign in, you will be ok. SteemConnect keeps your login info and the website your using just gets a code, so they never even see your keys. I wouldn't put my key in anywhere else. That being said, alot of these scam sites use a fake SteemConnect login, so you have to be careful and make sure that the url is correct and your browser shows the page as secure to make sure your not being duped.