In MXML files compiler cut all CDATA tags in XML. To resolve this problem use AS class Sample:
AS:
package
{
public class MyCDATAXML
{
public static var testSource : XML = <node> <![CDATA[<b>bold</b>
text]]>
</node>
}
}
MXML :
.....
<mx:TextArea htmlText="{MyCDATAXML.testSource"/>
....
