Imagine that I write my CV in a plain .txt file, but then add it to self-extracting rar and send it to you. If you open the file with notepad it will be kind of

Imagine that I write my CV in a plain .txt file, but then add it to self-extracting rar and send it to you. If you open the file with notepad it will be kind of unreadable. If you execute it, you can read the .txt file. Did you just broke my encryption? It is the same, they may send you the URL encrypted (more likely obfuscated), but then they also send you the code. In this case, they are giving you all you need to decrypt it. You just run their code that they sent to you. IANAL, but if I post my username/password here, I should not be able to sue you that you hacked my account.