OpenDroneMap-WebODM/app/static/app/js/css/Map.scss

.map{
    .leaflet-popup-content{
        .title{
            font-weight: bold;
            margin-bottom: 8px;
        }

        .asset-links{
            margin-top: 8px;
            padding-left: 16px;
        }
    }
}