Wanderer is a self-hosted trail database for saving and sharing adventures. Prior to 0.19.3, an authenticated user can store a crafted waypoint.icon value that createMarkerFromWaypoint() passes into FontawesomeMarker, where insertAdjacentHTML inserts the unvalidated value into map marker markup. Opening the affected trail map executes attacker-controlled script in the viewer's browser, which can expose session tokens or perform actions as the victim. Federated waypoint data can also reach the sink without a local account on the receiving instance. This issue is fixed in version 0.19.3.