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The Jinja2 sandbox can be used to evaluate untrusted code. Access to unsafe attributes and methods is prohibited.

Assuming env is a :class:`SandboxedEnvironment` in the default configuration the following piece of code shows how it works:

>>> env.from_string("{{ func.func_code }}").render(func=lambda:None)
>>> env.from_string("{{ func.func_code.do_something }}").render(func=lambda:None)
Traceback (most recent call last):
SecurityError: access to attribute 'func_code' of 'function' object is unsafe.


The Jinja2 sandbox alone is no solution for perfect security. Especially for web applications you have to keep in mind that users may create templates with arbitrary HTML in so it's crucial to ensure that (if you are running multiple users on the same server) they can't harm each other via JavaScript insertions and much more.

Also the sandbox is only as good as the configuration. We stronly recommend only passing non-shared resources to the template and use some sort of whitelisting for attributes.

Also keep in mind that templates may raise runtime or compile time errors, so make sure to catch them.

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