Is there an API for getting the current version of the extension?

Probably need refinement (extension id per say) but here is a starting point. It consists in loading the manifest as XML file and read the version value:

var xmlDoc = new window.XMLHttpRequest();
        var xmlFilePath = csInterface.getSystemPath(SystemPath.EXTENSION)+"/CSXS/manifest.xml";
        xmlDoc.open("GET",xmlFilePath,false);
        xmlDoc.send("");
        xmlDoc = xmlDoc.responseXML;
        var ext = xmlDoc.getElementsByTagName('Extension')[0];
        var version = ext.getAttribute ("Version");

HTH

Loic

Ozalto | Productivity Oriented - Loïc Aigon