Craft CMS 5.0.0-RC1 through 5.10.5 contains an incorrect authorization vulnerability. A control-panel user holding only the viewCategories permission (without saveCategories) for a category group can permanently modify that group's category structure — reordering and re-parenting categories — via the structures/move-element action. The structureEditable flag is computed from the view permission rather than the save permission, and the StructuresController authorizes the mutating action on that read-time session grant without a save re-check. Because a category's URI is derived from its position in the structure, moving a category changes its URL and those of its descendants and can corrupt navigation menus built from the category taxonomy. The issue is fixed in 5.10.6.

Craft CMS: Authorization bypass: view-only Categories user can modify category structure via structures/move-element