Show HN: Get encrypted data from people that don’t know how to encrypt
The weakest link I can identify here is MITM attacks when you're sending the link.Imagine:  Alice generates a link. 
  Sends the link to Bob over an unencrypted/unauthenticated link.
  Mallory intercepts the link. Generates his own link and send that link to bob.
  Bob enters the confidential information on Mallory's link.
  Mallory sees the confidential information, and then sends it to Alice's original link.

The only way to prevent this type of attack is sending the link over a secure channel. But if you already have a secure channel - what's the use case?