CVE-2026-46499: falha de média gravidade em CollaboraOnline online

Collabora Online is a collaborative online office suite based on LibreOffice technology. Prior to 24.04.18 and 25.04.11, several document operations delegated to `LibreOfficeKit` in the per-document kit process fail to enforce a session's read-only state. A read-only user, such as a viewer-role WOPI user, can send crafted `WebSocket` messages to execute document-mutating `UNO` commands and dialog operations despite the read-only interface. The changes can mislead co-viewers within the live session, or an authorized editor sharing the session can unknowingly save the modifications. The read-only attacker cannot save the document directly, and changes are discarded when the kit session ends unless an authorized editor saves them. This issue is fixed in versions 24.04.18 and 25.04.11.