**Description:** When type='keyvalue', the ‘application/x-www-form-urlencoded’ request header cannot be automatically added **Suggested Labels:** <!-- Optional comma separated list of suggested labels. Non committers can’t assign labels to issues, so this will help issue creators who are not a committer to suggest possible labels--> **Suggested Assignees:** <!--Optional comma separated list of suggested team members who should attend the issue. Non committers can’t assign issues to assignees, so this will help issue creators who are not a committer to suggest possible assignees--> **Affected Product Version:** all **OS, DB, other environment details and versions:** **Steps to reproduce:** 'io.siddhi.extension.io.http.sink.HttpSink#generateCarbonMessage' function, 'if (contentType.contains(mapType)) { httpHeaders.set(HttpConstants.HTTP_CONTENT_TYPE, contentType); }' logic vulnerability. **Related Issues:** <!-- Any related issues such as sub tasks, issues reported in other repositories (e.g component repositories), similar problems, etc. -->