A workaround is to disable the embedded jQuery and use an older version (for example, 1.11.1 which is the previous version the suite used): https://docs.telerik.com/devtools/aspnet-ajax/controls/scriptmanager/disabling-the-embedded-jquery

Repro steps:

1. put a wizard on the page that will do a postback upon step change
2. change a step

Expected: the postback occurs, the step is changed

Actual: Firefox throws TypeError: access to strict mode caller function is censored

Sample markup

        <telerik:RadWizard RenderMode="Lightweight" runat="server" ID="RadWizard1" Width="600px" Height="330px"
            RenderedSteps="Active">
            <WizardSteps>
                <telerik:RadWizardStep Title="first" Active="true">
                    in FF clicking on the next step will give you
                    <code>TypeError: access to strict mode caller function is censored</code>
                </telerik:RadWizardStep>
                <telerik:RadWizardStep Title="click for error in FF">This is caused by the need to do a postback and one thing that causes it is <code>RenderedSteps="Active"</code></telerik:RadWizardStep>
            </WizardSteps>
        </telerik:RadWizard>