If there is an extension for Firefox (for example) that retrieves data from any site whether the JS for a random website to obtain the same information by running the same query?
The question is vague and allows multiple interpretations.
\rInterpretation of the first.
If the extension of Fayerfoks gets data from a website, it is possible to change the JS code of the extension, thus, to obtain similar information for a random other site?
Maybe you can... but maybe not released.
It depends on the shape and purpose of the request.
A simple example is the expansion of the "Abrahamic", which on Habrahabr gets the value of the karma rating through abrahamovce API. And it will not allow you to get the rating value on the website FreeLance.Ru by running the same query
— because "Freelance" nope because same
Another example: imagine an extension that gets the icon of the site using a common Protocol, that is, first it downloads the front page, then looks in her element
) and picks out from it the URL of the icon. This extension will allow you to obtain a badge from another site using the same query
— because the Protocol is the same.
\rThe interpretation of the second.
If the extension of Fayerfoks gets data from a website, it is possible to implement some random other site Java script that will work on the website and get this website the same information that is received by the JS code of the extension working in Fayerfoks?
The answer is likely negative. In the browser applies the requirement of common descent
in relation to Java script and the resources to which Java script refers. Accordingly, if the website from which the data is received, not taken special measures