Guests cannot change their username and password is not relevant in the resource tenant (credentials are managed in the "home" tenant). You can restrict them from performing other actions, seeing group membership, etc. Read here: https://learn.microsoft.com/en-us/azure/active-directory/enterprise-users/users-restrict-guest-permissions
how to restrict deafult guest user to edit his own profile on azure

Mark
21
Reputation points
Hi all, is there any possible to avoid my default guest user to edit his own profile like username , password etc...
or else i want to add user as guest that user can't edit his profile.
Accepted answer
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Vasil Michev 66,591 Reputation points MVP
2021-04-13T14:19:18.503+00:00 0 additional answers
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You cannot block anyone from changing their own password in Azure AD/O365. What I was saying above is that it doesnt really matter if a Guest can change his password in your tenant, as they still need to use the credentials from their home tenant to login.