Potential Information Leak in User-Constructed Message Templates in nonebot2

nonebot2 is a cross-platform Python asynchronous chatbot framework written in Python. This security advisory pertains to a potential information leak (e.g., environment variables) in instances where developers utilize `MessageTemplate` and incorporate user-provided data into templates. The identified vulnerability has been remedied in pull request #2509 and will be included in versions released from 2.2.0. Users are strongly advised to upgrade to these patched versions to safeguard against the vulnerability. A temporary workaround involves filtering underscores before incorporating user input into the message template.