A couple of years ago, there was a big breach at LinkedIn which resulted in the theft of account credentials. The theft of the credentials allowed cybercriminals to focus on new targets, as the credentials could provide them access to restricted environments.
But it is not only the access to the restricted environments which should worry you, the cybercriminals which got their hands on the credentials are now able to login at stolen LinkedIn accounts, allowing them to map the environment so they can select targets for future / current hacking operations.
Now there have been a lot of posts which claim that you should change your LinkedIn password, but I think it is more important to understand that Two-factor authentication is the only way to be certain that your account is not being misused.
You can enable your LinkedIn Two-factor authentication by following these steps: