Affected: wekan

Wekan is open source kanban built with Meteor. Prior to 9.89, the second Boards.allow({ update }) rule in server/permissions/boards.js called canUpdateBoardSort in server/lib/utils.js, which authorized any board member whenever fieldNames included sort. Because Meteor combines allow rules with OR semantics and applies the complete modifier, a comment-only or read-only member could send one Boards.update with $set values for sort, members, permission, and title, make themselves the sole board administrator, expose a private board, and evict the legitimate owner; the last-admin deny rule inspected only $pull and did not block a wholesale $set of members. Version 9.89 requires sort to be the only modified field and rejects $set member arrays that remove the last active administrator. This issue is fixed in version 9.89.