For code that runs on the client / browser side, you can only use the _id field as a request. On the server, you can run it as you wish.
Change your code to get the document first, and then use its _id to update.
var person = People.findOne(t.data); People.update({_id: person._id}, {$set: {name: e.currentTarget.value}});
I assume t.data is some kind of query? If its _id try using {_id: t.data as a query. In any case, as long as the update selector only uses _id , this should be fine.
The reason this could affect the tutorial that you are following is because this change was introduced recently to block security.
Akshat
source share