CVE-2026-62851: FreeScout: Cross-mailbox conversation existence / internal-id disclosure via the search-by-number (`#`) shortcut (missing mailbox authorization)

FreeScout is a self-hosted help desk and shared mailbox. Prior to 1.8.226, the search-by-number shortcut in ConversationsController::search() resolves a user-controlled ticket number without applying the mailbox filter or view policy used by the normal search path. An authenticated non-admin agent who is a member of at least one mailbox can request /search with a hash-prefixed ticket number and use the 302 Location header to confirm that a conversation exists in a different mailbox the agent cannot access and learn its internal conversation and folder identifiers. The destination conversation remains protected, so this issue does not disclose message content, attachments, or customer data. This issue is fixed in version 1.8.226.