Starting with macOS 10.10 apple advises us to use the newer WKWebView Apple Developer Documentation instead of WebView.
There’s a feature request for this: <https://xojo.com/issue/52330>
Since 10.9 support is now deprecated in Xojo: http://developer.xojo.com/system-requirements it would seem like this is a good time to make the switch.
In the mean time, is there any way to use WKWebView now? Does MBS plugins offer a control that does this?