I have crossdomain.xml in document root of my site with the following contents:
<?xml version="1.0"?>
<!DOCTYPE cross-domain-policy SYSTEM "http://www.macromedia.com/xml/dtds/cross-domain-policy.dtd">
<cross-domain-policy>
<allow-access-from domain="*.doubleclick.net" />
</cross-domain-policy>
This is because I want adsense advertisers using rich-media ads to see my website content in order to load correct ads.
I then check my site on detectify.com and gave me this warning about the file:
Wildcard crossdomain.xml Policy
What does this mean?
The crossdomain.xml policy file allows SWF files hosted at subdomains to interact with the domain.
What can happen?
If the attacker are able to upload a SWF at any of the subdomains or otherwise get control however a subdomain the attacker can bypass CSRF-protections at the domain and depending on the application read sensitive data.
My question is what should I really do?
Will hackers do some serious damage even though my website does not contain shockwave flash files (except for those advertisers put in the ad units)? If so, then I should remove it. But if my income drastically reduces as a result from the ad not being properly served due to a missing crossdomain.xml file, then I feel I need the file in place.
What should I do here?