OpenSearchServlet does not check text-to-output for illegal xml characters; dependent on search result, its possible for OSS to output xml that is not well-formed. For example, if text has the character FF character in it – -- i.e. the ascii character at position (decimal) 12 – the produced XML will show the FF character as '' The character/entity '' is not legal in XML according to
http://www.w3.org/TR/2000/REC-xml-20001006#NT-Char
.