On my HTML page I am using a javascript from an external source (I cannot modify it). On executing my HTML page, it displays some data, different on every user's ip. What I want to do is create another javascript on that page, so after the first external script gots processed and displays the data, this new one should extract that data and pass it by forward to a php form hidden input or something like that, so I can process it more, depending on the resulted data from the first script. What do you think about this?
I guess that the first javascript is inserting their data on his own iframe from a different site as yours. If yes, your second javascript won't access that data because cross-site scripting is not allowed by default .