Anonymize only Child Nodes

Hello, I was wondering could anyone help me figure out the sed script required and regex to Anonymize child nodes from xml - The difficulty seems to be due to the fact each node takes it's own line within splunk rather than usual single line ` 123 `. Here is an example of how it appears: 123 And the appearance I would want would be something like: xxxx Any help would be great with this - thank you. James