security: Fix Multiple XSS Vulnerabilies

It may be possible to steal or manipulate customer session and cookies,
which might be used to impersonate a legitimate user, allowing the hacker to
view or alter user records, and to perform transactions as that user.
Sanitation of hazardous characters was not performed correctly on user
input.

osTicket did not properly sanitize array values in `Format::htmlchars()`.
Some values in the Admin Interface were not properly sanitized and returned
to the response.