ERROR: 'Length limit reached'

This message frequently appear in our Jetty's logs:

ERROR: 'Length limit reached'

No timestamp of stack trace whatsoever

The only reference to this error message I've been able to find is in https://github.com/xwiki/xwiki-commons/blob/master/xwiki-commons-core/xwiki-commons-xml/src/main/java/org/xwiki/xml/ExtractHandler.java