What is crossdomain.xml and what is it needed for?
 

I cant find any articles newer than 2008 in google could someone explain in common terms what it is and the uses for it?

it allows you to use a xml fie from a foreign domain to yours

could be for an ajax call in javascript from another domain

im getting alot of 404 errors for /crossdomain.xml for all the wordpress installs on a certain host, i was hoping it was surfers looking for something :(

You would need a crossdomain.xml to allow your flash swf file to import swf files from
another domain. Which you don't want to do unless the other domain is yours or
extremely trusted.

The 404 error you are getting is probably a "sniffer" trying to find and hack the
file.

someones using a really outdated vuln scanner

:thumbsup

as far as i know,
if you permit other domains in crossdomain.xml and your flash player has preroll ads.,

then i can download your flashplayer, do reverese engg., in it remove the preroll ads script, upload it to my server and still fetch videos from your box.

but i may be wrong.

That "can" work, but that's more work than needed to leach videos in most cases,
and you wouldn't need to have your domain in their crossdomain.xml either.

Videos are "played" rather then "imported" so no crossdomain.xml is needed to
play videos from other domains.

They use it in Kaltura video server for letting the flash player play at any domains in the list...

http://www.kaltura.org/solving-crossdomainxml-issue

Just check how youtube does it.