Cross-Site Scripting Attacks Possible At Multiple Webspace Providers

["Matthew Murphy" <mattmurphy () kc rr com>]

Issue: Multiple web space providers are susceptible to script-based origin
validation attacks.
Impact: Cookie theft, page manipulation, ...
Additional Information: http://www.murphy.101main.net/vulns/2002-24.txt

Many web space providers offer their users web space by way of a
folder-based URL, something like this:

http://www.domain.com/community/uid

An interesting scenario occurs when pages are visited on (commonplace)
JavaScript-enabled browsers.  The same-origin policy that is used to avoid
cross-frame security violations is completely compromised, as the only
difference in these URLs to the browser is folder/virtual paths, not
sufficient for a same-origin violation.  This vulnerability allows anyone
who can create a webspace account on the host to manipulate the appearance
of other hosted sites provided the victim can be coaxed to a page under
their control.

This allows for typical cross-domain scripting attacks (stealing cookies,
reading form data, ...), which could be pretty devastating, as one site
instantly has access to the guts of a few thousand (million?) others.

I have confirmed that Terra Lycos' AngelFire service is vulnerable, and also
Yahoo! Geocities is believed susceptible.  It is very likely that others are
vulnerable.

"The reason the mainstream is thought
of as a stream is because it is
so shallow."
                     - Author Unknown