luci-app-tailscale-community - Command Injection via tailscale.do_login RPC

luci-app-tailscale-community contains a command injection vulnerability in the tailscale.do_login RPC method that allows authenticated users to execute arbitrary commands as root. The vulnerability exists because user-controlled loginserver and loginserver_authkey parameters are improperly quoted within a double-quoted shell command, allowing shell substitutions like $() to be evaluated by the outer shell before argument processing.