The Travel Tracker is a Wikivoyage tool that allows users to track which countries/territories they have visited. It can be used by all logged-in users by default (you don't need to be an active contributor) – simply use Special:MyPage/Visited (no additional scripts required) – non-logged-in users (i.e. temporary accounts) will not be able to create such a tool.
The data and mapshapes used is sourced from Wikidata, which in turn is sourced from OpenStreetMap. Wikivoyage officially takes no side in any political disputes – when possible, the tool follows whatever has been agreed upon for Wikivoyage per Wikivoyage:Be fair#Political disputes; however, this isn't always possible due to the tool fetching mapshapes from OpenStreetMap which has its own set of guidelines for dealing with political disputes.