If you configure your browser not to allow the client to leak anything, it doesn't even matter if the client has been modified because it can't leak anything an

If you configure your browser not to allow the client to leak anything, it doesn't even matter if the client has been modified because it can't leak anything anyway. EDIT: I'm speaking from the position of an end-user. I'm downloading ciphertext + a decryption tool from an untrusted server and executing the decryption tool locally, with a key which I input locally. I want to make sure that the plaintext and key do not get leaked back to the server. Situations where this arises include encrypted pastebins, bitaddress.org, Ian Coleman's BIP39 tool, anything else that generates or handles bitcoin keys, etc.