U+FFFE and U+FFFF characters can block JSF applications by rendered as ajax response

[halcsi19790320]

Theese characters are valid UTF-8 characters, but can cause error, if server send this value to browser as ajax response.
Browser's cannot parse theese characters.

Remove non-xml character from Request with converter, or default validator with RenderResponse patch?

stackowerflow link

The problem is issued 4 four years ago, but I think there are 2 more characters.

Old issue

[BalusC]

--> #5464