Use jQuery - Blog - The jQuery Cross-Domain Ajax Guide. With "JSON with padding" you can request JSON formatted data from a 3rd party server.
It makes usage of the script tag. Read more about it in the This allows us to query any web API that returns JSON and allows a callback. In this quick example we query the Twitter API to find out the followers number of the @usejquery account. For further reading check out the article How to build a personal mashup page with jQuery . Security Compass - Application Security. 23C3: Subverting AJAX. 23rd Chaos Communication Congress Who can you trust?
Next generation vulnerabilities in 2.0 Web Applications Ajax and the new dynamic extensions leverage new threats that lead to innovative attack scenarios against web applications.