habitica-self-host/migrations/find_unique_user.js

// mongo habitrpg ./node_modules/lodash/index.js ./migrations/find_unique_user.js

/**
 * There are some rare instances of lost user accounts, due to a corrupt user auth variable (see https://github.com/lefnire/habitrpg/wiki/User-ID)
 * Past in the text of a unique habit here to find the user, then you can restore their UUID
 */

db.users.find().forEach(function(user){
  user.tasks = user.habits.concat(user.dailys).concat(user.todos).concat(user.rewards);
  var found = _.some(user.tasks, {text: ""})
  if (found) printjson({id:user._id, auth:user.auth});
})