Add warning about untrusted private keys
diff --git a/docs/hazmat/primitives/rsa.rst b/docs/hazmat/primitives/rsa.rst
index 3c509cf..d62aa10 100644
--- a/docs/hazmat/primitives/rsa.rst
+++ b/docs/hazmat/primitives/rsa.rst
@@ -16,6 +16,13 @@
Normally you do not need to directly construct private keys because you'll
be loading them from a file or generating them automatically.
+ .. warning::
+ This method only checks a limited set of properties of its arguments.
+ Using an RSA that you do not trust or with incorrect parameters may
+ lead to insecure operation, crashes, and other undefined behavior. We
+ recommend that you only ever load private keys that were generated with
+ software you trust.
+
This class conforms to the
:class:`~cryptography.hazmat.primitives.interfaces.RSAPrivateKey`
interface.