In v11, go to the Widgets application and find the widget in question. On the General tab of that widget, look to see what web part the widget is "based on". Next, go to the Web Parts application and find that web part. The web part will have a location in the file system where you can find the code/ The starting path is typically /CMSWebparts.
If it is a base Kentico web part, I'd highly suggest NOT modifying the base web part and/or layout and looking further to find where those properties may be set. You should report back with what web part the widget is based on and we can troubleshoot further from there.