We were told to send an email with a link to the users. The users will get a token in the URL where they will be able to chose some options and post their selection. Example URL: https://example.com/DoSomething?token=wer545w5e54r
The application is being made in MVC .Net, Web API and is hosted in a server with https.
Currently, we are validating if the token exists we accept the transaction otherwise we are returning 401 error.
Could you tell me what are the security points that we consider on in order to make secure our application?
Our client does not want to deal with a sign-in form