Hi @CeliaM, thanks for messaging the Community!
If a person's email is hacked, then any information in that email is considered compromised. This would include the resetting of passwords, logins to most websites, and the shared links to Dropbox files and folders.
Depending on the plan of the owner of the shared link, there could be a password on the link. Assuming this password wasn't shared via the same email, then the link could be considered secure.
If you have any further queries, feel free to message back.