Zammad is a web based open source helpdesk/customer support system. Prior to 7.1.2, any authenticated user can call the REST endpoint for getting a tag list and receive the tag names for the given ticket, regardless of whether they have access to that ticket. Tags are an internal categorization feature and may contain sensitive labels. Ticket IDs are sequential integers, making bulk enumeration straightforward. This issue is fixed in version 7.1.2.