We currently have a team of 25 - working on over 15 secured website (These Websites are subscription based which is purchased under the company name)

I am looking for a way, where we can only allow them access to the website via any software or third-party application without giving login/password details to them. In other sense, I don't want to give them the login/passwords, Ideally looking for a software/application where they can access those websites without any information of Login/passwords given to them.
e.g * a password protected software/application, that goes auto-login once they start working without them knowing the passwords *

(they might misuse our subscriptions OR use/sell our logins to other parties)

This is just to stay at the safe side of any info being leaked internally.

Any suggestions?
Really need this solution (tried through many mediums, Cant get a solution)