Fix typo in doc and copy missing warning
diff --git a/include/mbedtls/aes.h b/include/mbedtls/aes.h
index 731e568..104c8f5 100644
--- a/include/mbedtls/aes.h
+++ b/include/mbedtls/aes.h
@@ -349,6 +349,10 @@
* Note that for both stategies, sizes are measured in blocks and
* that an AES block is 16 bytes.
*
+ * \warning Upon return, \p stream_block contains sensitive data. Its
+ * content must not be written to insecure storage and should be
+ * securely discarded as soon as it's no longer needed.
+ *
* \param ctx The AES context to use for encryption or decryption.
* \param length The length of the input data.
* \param nc_off The offset in the current \p stream_block, for