Follow @Openwall on Twitter for new release announcements and other news
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date: Thu, 20 Apr 2023 12:57:18 +0200
From: Stefano Di Paola <>
Subject: Re: Checking existence of firewalled web servers in
 Firefox via iframe.onload

Hello George,

from time to time it happens to rediscover techniques issues.
This is one of those times :)

In 2006 there has been a lot of interest around browser based port
scans, in particular to pivot internal networks.

The following links are some of them:

Some of those thecniques have been mitigated, and some it's still

There are surely other resources IIRC, although some of them might have
been deleted, such as the ones on which is a real pity..


Ps. this email applies to the other Script technique thread/email as

On Tue, 2023-04-18 at 15:59 +0300, Georgi Guninski wrote:
> In short in Firefox 112, it is possible to check existence
> of firewalled web servers. This doesn't work in Chrome and Chromium
> 112
> for me.
> If user A has tcp connection to web server B, then in the
> following html:
> <iframe src="http://B" onload="load()" onerror="alert('error')"
> id="i1" />
> the javascript function load() will get executed if B serves
> valid document to A's browser and will not be executed otherwise.
> This work for both http and https, and for http it is allowed
> B to be IP address. Under some configurations of Apache2,
> it serves http despite having https configured.
> In some sense, this is close to nmap via javascript in a browser.
> Potential privacy implication is when the attacker guess the
> range of firewalled IPs and check them all in a loop.
> For online test:
Stefano Di Paola
CTO/Chief Scientist IMQ Minded Security
Software & Security Engineer


Powered by blists - more mailing lists

Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.

Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.