The AssertEdit extension (deployed on wikidata and other wmf wikis) adds the assert param to the api edit modules to help ensure bots do not edit logged out and other such stuff.
Wikibase api modules, however, do not recognize the assert param.
AssertEdit uses the APIEditBeforeSave hook in ApiEditPage. It also uses APIGetParamDescription and APIGetAllowedParams which are in ApiBase.
Version: master
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=27841