Posted By: Anonymous
Why does Google prepend
while(1); to their (private) JSON responses?
For example, here’s a response while turning a calendar on and off in Google Calendar:
while (1); [ ['u', [ ['smsSentFlag', 'false'], ['hideInvitations', 'false'], ['remindOnRespondedEventsOnly', 'true'], ['hideInvitations_remindOnRespondedEventsOnly', 'false_true'], ['Calendar ID stripped for privacy', 'false'], ['smsVerifiedFlag', 'true'] ]] ]
I would assume this is to prevent people from doing an
eval() on it, but all you’d really have to do is replace the
while and then you’d be set. I would assume the eval prevention is to make sure people write safe JSON parsing code.
I’ve seen this used in a couple of other places, too, but a lot more so with Google (Mail, Calendar, Contacts, etc.) Strangely enough, Google Docs starts with
&&&START&&& instead, and Google Contacts seems to start with
What’s going on here?
Contrived example: say Google has a URL like
mail.google.com/json?action=inbox which returns the first 50 messages of your inbox in JSON format. Evil websites on other domains can’t make AJAX requests to get this data due to the same-origin policy, but they can include the URL via a
<script> tag. The URL is visited with your cookies, and by overriding the global array constructor or accessor methods they can have a method called whenever an object (array or hash) attribute is set, allowing them to read the JSON content.
&&&BLAH&&& prevents this: an AJAX request at
mail.google.com will have full access to the text content, and can strip it away. But a
This does not address the issue of cross-site request forgery.