adding legacy-widget error

trying to add the legacy-widget to one of the widget areas - I do not get the text widget as an option - checked the console in safari and I see the following error: "Error while parsing the 'sandbox' attribute: 'allow-orientation-lock', 'allow-presentation' are invalid sandbox flags."

any idea where that is coming from and how to fix this - disabled all the plugins, still the same error.

any help is very much appreciated.

Thanks