The structure of runtime build parameters in the XML API for builds has changed in 1.652
Retrieving XML for a job using /job/JobName/api/xml?depth=2
In 1.651 the parameters are returned in the following structure:
In 1.652 (and 1.653) the parameters are returned in the following structure:
The <parameter> part of the output has disappeared. I do not see any reference to this in the changelog so I assume this is a regression and not an intentional change.