Moving a user's task to change the status assigns it to the current user

In the agile board, work mode, with swimlanes by assignee, while working a scrum master:

I drag + drop an issue from one column to another column to change the issue state, for example from "Open" to "In Progress". The issue state is changed, but the issue is also assigned to me, the current user. This is a bug, because the UI indicates that the issue will stay in the current swimlane and the issue state will be modified.