Using a vulnerability in the Dota 2 client, hackers launched a script that constantly sent invitations to a team or guild - due to the frequency of requests, it was impossible to block them. At the same time, after accepting the invite, the attacker instantly left the group and continued to spam. With the new patch, the client will automatically decline team invites when searching for a match.
To withdraw skins from Hellcase, players send trade requests directly from Hellcase to their Steam inventory. Hellcase doesn't do direct money transfers. To withdraw your cash from Hellcase, you'll need to use one of the many partnered third-party websites like ShadowPay. Both processes work as long as you follow the Steam trading rules, you have the right items, and your account is configured correctly.