SharePoint - Stop sharing - new behavior or new bug?

I can't say whether this is a deliberate change or a bug, so take this as context rather than a confirmed answer. The standard Contribute permission level doesn't include Manage Permissions, and removing sharing from an item means resetting its unique permissions, which is a Manage Permissions action. So if the Stop sharing button is now greyed out for Contribute users, that would line up with the documented permission levels, even if it used to be more lenient. Things worth checking: 1) Does Manage access on that file still let the sharer remove the one wrong recipient? If not, a site owner can do it from the same panel. 2) In Site settings > Site permissions > Change how members can share, see whether sharing is set to site owners only, or owners and members, since that changes who can share and who can undo it. 3) Test with a second account at Contribute and another at Edit/Member to compare. If it differs from what you saw last month, open a support ticket and check the Message Center for a sharing change notice, because that is the only reliable way to confirm a rollout change. For the accidental-share case, the quickest fix today is a site owner removing the recipient directly.