An issue was discovered in Jinja2 2.10. The from_string function is prone to Server Side Template Injection (SSTI) where it takes the "source" parameter as a template object, renders it, and then returns it. The attacker can exploit it with {{INJECTION COMMANDS}} in a URI. NOTE: The maintainer and multiple third parties believe that this vulnerability isn't valid because users shouldn't use untrusted templates without sandboxing