Hikka vulnerable to RCE through dangling web interface

Summary

Hikka, a Telegram userbot, has vulnerability affects all users on all versions of Hikka. Two scenarios are possible. 1. Web interface does not have an authenticated session: attacker can use his own Telegram account to gain RCE to the server by authorizing in the dangling web interface. 2. Web interface does have an authenticated session: due to insufficient warning in the authentication message, users were tempted to click "Allow" in the "Allow web application ops" menu. This gave an attacker access not only to remote code execution, but also to Telegram accounts of owners. Scenario number 2 is known to have been exploited in the wild. No known patches are available, but some workarounds are available. Use `--no-web` flag and do not start userbot without it; after authorizing in the web interface, close the port on the server and/or start the userbot with `--no-web` flag; and do not click "Allow" in your helper bot unless it is your explicit action that needs to be allowed.