CVE-2026-50279: Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap

EntriesController::actionSaveEntry() performs entry-edit permission checks before request-controlled author changes are applied to the model. The subsequent author mutation path accepts attacker-supplied authors / author parameters and allows the change when the current user is one of the old authors. Because the controller does not re-run authorization after mutating the author list, a low-privileged user can reassign an entry’s authorship to another user without holding the dedicated peer-author-change permission.