Hello, For information, this bug is fixed in firefox 58, available in beta version in experimental, so people might want to already pick it up from there.
> Impact: An AT that controls navigation (like the Orca screen reader) is > often presenting content which is not visible -- no problem for a user who > is blind and working alone. But if the Orca user is working with a sighted > peer, or using Orca along with magnification software which tracks the caret > location, that peer or low vision user cannot see what is being presented." Samuel
