Home/ Questions/Q 8972223
In Process

The Archive Base Latest Questions

Editorial Team
  • 0
Asked: 2026-06-15T18:09:58+00:00

I’m wondering what is the reason for using following JSONP response syntax: Under URL:

  • 0

I’m wondering what is the reason for using following JSONP response syntax:

Under URL: https://ect.channel.facebook.com/probe?mode=stream&format=json

There is:

for (;;); {"t":"heartbeat"}
{"t":"heartbeat"}
{"t":"continue","seq":0}

My question is, what exactly does for(;;); in this JSONP response. How is it parsed?

Share

Leave an answer

You must login to add an answer.

Need An Account,

1 Answer

  1. Editorial Team

    This isn’t JSONP; it’s JSON which is delibaretly modified to fail if used as JSONP.

    If you include that URL in a <script> tag, it will freeze the browser in an infinte for loop.

    This prevents attackers from including it in an external site and calling Object.defineProperty to create a setter function and bypass the SOP.

    • 0