Security aspects of second-level domains like .co.uk

What are the security aspects of second-level domains like .co.uk?

Especially,开发者_开发知识库 when it comes to cross-site scripting and cookies stealing. Many of basic security mechanisms on client rely on different 2nd-level comain names. Does a developer keep special attention when developing for e.g. foo.co.uk?

Browsers are using a list of effective TLDs, instead of relying only on the level of the domain, for things such as allowing sites to set a cookie.

See http://publicsuffix.org/list/ . As seen here, this is used by Firefox, Chrome and Opera.