A missing authentication vulnerability exists in the Altium 365 SearchService. A legacy SOAP endpoint exposes search index operations without requiring authentication, session tokens, or any form of identity verification. An unauthenticated network attacker who can reference a target workspace's identifier can interact with that workspace's search index, crossing tenant boundaries. Successful exploitation allows reading a workspace's indexed contents (such as component data, project and folder names, and user metadata) and injecting, modifying, or deleting search index entries. These operations affect the search index only, not the underlying vault data, but they can disclose sensitive workspace information and compromise the integrity and availability of search results. Altium 365 cloud deployments are affected; on-premise Altium Enterprise Server is not affected.