fof/byobu is a private discussions extension for Flarum forum. Affected versions were found to not respect private discussion disablement by users. Users of Byobu should update the extension to version 1.1.7, where this has been patched. Users of Byobu with Flarum 1.0 or 1.1 should upgrade to Flarum 1.2 or later, or evaluate the impact this issue has on your forum's users and choose to disable the extension if needed. There are no workarounds for this issue.