> -----Original Message-----
> From: Watchfire Research [mailto:security-research@xxxxxxxxxxxxx]
> Sent: Wednesday, December 21, 2005 4:06 PM
> To: bugtraq@xxxxxxxxxxxxxxxxx
> Subject: XSS vulnerabilities in Google.com
>
> //=====================>> Security Advisory <<=====================//
>
> ---------------------------------------------------------------------
> XSS vulnerabilities in Google.com
> ---------------------------------------------------------------------
>
> --[ Author: Yair Amit , Watchfire Corporation
> --[ Discovery Date: 15/11/2005
> --[ Initial Vendor Response: 15/11/2005
> --[ Issue solved: 01/12/2005
> --[ Website: www.google.com
> --[ Severity: High
>
> --[ Summary
>
> Two XSS vulnerabilities were identified in the Google.com website,
> which allow an attacker to impersonate legitimate members of Google's
> services or to mount a phishing attack.
> Although Google uses common XSS countermeasures, a successful attack
> is possible, when using UTF-7 encoded payloads.
>
> --[ Background
>
> Google's URL redirection script
> ---------------------------------------------------------------------
>
> The script (...) is normally used for
> redirecting the browser from Google's website to other sites.
>
> For example, the following request will redirect the browser
> to :
> -
>
> When the parameter (q) is passed to the script with illegal format
> (The format seems to be: ), a "403 Forbidden" page
> returns to the user, informing that the query was illegal.
> The parameter's value appears in the html returned to the user.
>
> If is requested, the text in
> the "403 Forbidden" response would be:
> - "Your client does not have permission to get URL
> /url?q=USER_INPUT from this server."
>
> The server response lacks charset encoding enforcement, such as:
> * Response headers: "Content-Type: text/html; charset=[encoding]".
> * Response body: "<meta http-equiv="Content-Type" (...)
> charset=[encoding]/>".
>
> Google's 404 NOT FOUND mechanism
> ---------------------------------------------------------------------
>
> When requesting a page which doesn't exist under www.google.com, a
> 404 NOT FOUND response is returned to the user, with the original
> path requested.
>
> If is requested, the following text
> appears in the response:
> "Not Found
> The requested URL /NOTFOUND was not found on this server."
>
> The server response lacks charset encoding enforcement, such as:
> * Response headers: "Content-Type: text/html; charset=[encoding]".
> * Response body: "<meta http-equiv="Content-Type" (...)
> charset=[encoding]/>".
>
> --[ XSS vulnerabilities
>
> While the aforementioned mechanisms (URL redirection script,
> 404 NOT FOUND) escape common characters used for XSS, such as <>
> (triangular parenthesis) and apostrophes, it fails to handle
> hazardous UTF-7 encoded payloads.
>
> Therefore, when sending an XSS attack payload, encoded in UTF-7, the
> payload will return in the response without being altered.
>
> For the attack to succeed (script execution), the victim's browser
> should treat the XSS payload as UTF-7.
>
> --[ IE charset encoding Auto-Selection
>
> If 'Encoding' is set to 'Auto-Select', and Internet-Explorer finds a
> UTF-7 string in the first 4096 characters of the response's body,
> it will set the charset encoding to UTF-7 automatically, unless a
> certain charset encoding is already enforced.
>
> This automatic encoding selection feature makes it possible to mount
> UTF-7 XSS attacks on Google.com.
>
> --[ Solution
>
> Google solved the aforementioned issues at 01/12/2005, by using
> character encoding enforcement.
>
> --[ Acknowledgement
>
> The author would like to commend the Google Security Team for their
> cooperation and communication regarding this vulnerability.
>
