When you view a Browsers report, sometimes it contains a browser with an unknown version.
Adobe Analytics uses a lookup table to populate the browsers report. These lookup table entries are version-specific. Therefore, when an organization (such as Mozilla) updates their browser, Analytics doesn't recognize the exact version used. When this event occurs, it specifies the general browser followed with (Unknown Version).
Adobe's lookup tables are updated in the maintenance release after any major browser update, following a standard development cycle. If you want to be notified when a particular browser version is updated on Adobe's lookup tables, have a supported user contact Customer Care. Include the browser and version, and the Adobe representative can create an incident that updates when the maintenance release is complete.