It was pointed out in T88397[1] that a list=search query was populating the 'redirecttitle' output property as an object containing the internal members of a MediaWiki Title object, where a string containing the prefixed title is more likely what was intended.

Any clients relying on this output property should be updated to deal with the corrected value.

This will be deployed to WMF wikis with 1.25wmf16, see https://www.mediawiki.org/wiki/MediaWiki_1.25/Roadmap for the schedule.

[1]: https://phabricator.wikimedia.org/T88397