GQL entry mutation siteId bypasses schema site scope, enabling cross-site content read/write/delete.

Craft CMS GraphQL entry mutation resolvers (saveEntry, deleteEntry) read siteIddirectly from$argumentswithout passing throughArgumentManagerprepareArguments(), which is the function that enforces site-scope filtering via array_intersect against the GraphQL schema’s allowed sites. The query path (ElementResolverprepareElementQuery) correctly calls prepareArguments()`, so queries to unauthorized sites return empty. But mutations bypass this entirely — an attacker with a token scoped to Site A can create, modify, or delete entries in Site B by passing siteId in the mutations argument.

• Confidentiality: saveEntry loads the element by siteId — attacker can read content from unauthorized sites.
• Integrity: saveEntry writes to the specified site’s elements_sites record; propagation spreads changes to all sites.
• Availability: deleteEntry locates the element by siteId, then calls deleteElementById without siteId, deleting the element across all sites.