Unable to add an Open Spatial Consortium (OGC) Web Feature Service (WFS) to ArcGIS Online Map Viewer when adding access credentials as additional parameters.

Workaround

Add the WFS in Map Viewer Classic with the additional parameters and the issue will not occur:

1) In an empty Map Viewer Classic map, click + Add then click Add Layer from Web.

2) Under 'What type of data are you referencing?', select A WFS OGC Web Service.

3) Paste the URL of the WFS and then add the two additional parameters.

Steps to Reproduce