Firefox wyciwyg-scheme questions

[vzjrz]

Go here: http://marry-mind.deviantart.com/art/Faceless-Void-Death-Prophet-556598001

These are my current rules:

Try clicking on the download button in the top-right corner. A blank window opens with nothing displayed and umatrix shows a weird wyciwyg-scheme I've never seen before.

Reading a little more into this it seems to be part of firefox's cache but I'm wondering if it's safe to add matrix-off: wyciwyg-scheme true to my rules?

[0xBRM]

https://en.wikipedia.org/wiki/WYCIWYG
Yes

[gorhill]

Fixed with e8136cb.