Warn that overriding __builtins__ for eval is not a security mechanism

[StanFromIreland]

This misleads users as it gives the impression that the above warning can be ignored.

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📚 Documentation preview 📚: https://cpython-previews--145773.org.readthedocs.build/

[sethmlarson]

LGTM, thank you!

[nedbat]

Suggested change

	user-supplied input will lead to security vulnerabilities.
	un-trusted user-supplied input can easily lead to security vulnerabilities.

[StanFromIreland]

We are generally trying to strengthen the warning (we held a little vote, people are in favour), but IMO this suggestion reverts that. Might I ask why exactly you want it to be so?

[nedbat]

Suggested change

	names, but it is **not** a security mechanism, the executed code can
	still access builtins.
	names, but is **not** a security mechanism: the executed code can
	still access all builtins.

[nedbat]

Suggested change

	names, but it is **not** a security mechanism, the executed code can
	still access builtins.
	names, but this is **not** a security mechanism: the executed code can
	still access all builtins.

[nedbat]

Suggested change

	user-supplied input will lead to security vulnerabilities.
	un-trusted user-supplied input can easily lead to security vulnerabilities.

[picnixz]

I'm always torn when we change these kind of notes. I don't agree that this will lead to security vulnerabilities. It depends on your threat model. So the "may"/"can" formulation is for me the correct one.

What I do find correct however is that untrusted input can lead to security vulnerabilities. I would honestly drop the "easily" part as again it depends on where the untrusted input comes from. For instance, the user can supply an arbitrary string, and that arbitrary string is processed with (highly non-trivial, but still polynomial-time evaluable) reversible transformations that eventually output a string that is then evaled. In this case, you can consider that you have a security vulnerability, but not necessarily "easily" achievable (but still achievable if you spend time to reverse the transformations).