It is believed that the moment we insert our private key to gain access to our MyEtherWallet wallet, at this time the network is very vulnerable to hacking by all sorts of hackers. There is probably some danger, but I always use only secret keys and so far there have been no problems. True, for this I do not copy the secret key code, but type it manually from a note on paper. Or I store it in electronic form with certain changes in several symbols. I insert it, and then I make the necessary changes in place. This greatly reduces the overall risk of outside access to the private key.