Navigating to a Diffusion commit, and selecting the option to edit that commit, can in some circumstances bring you to the edit page for a descendant of that commit.
Create a Diffusion repository. Make two commits directly via git, (...a1) and (...b2). b2 is HEAD and a1 is its parent.
Navigate to /r....a1. Select "Edit Commit". Note that the browser navigates to /diffusion/.../commit/...a1/edit/
But the breadcrumbs show <Diffusion Icon> -> <Repo Name> -> ...b2. Editing the fields and hitting save does indeed modify ...b2, not ...a1 as expected.