Run JS on third party page

Question

I would like to know all possible ways how to run a JS(site) on a third-party page, where my real intention is to manipulate the frontend even to give me the custom view of a page x.

I can already do this using the program Fiddler where it is possible through the resource "Autoresponder" i replace the existing JS or CSS on a page by my local files, but I would like to know according to the experience of anyone who knows...what other ways to do this?

Answer 1

You can inject Javascript into pages using a feature called Userscripts. This is quite used, including, the Github organization with Stackoverflow members in English has some scripts that we developed to assist us on a day-to-day basis. You can see more details on this publication of the goal.

You can use extensions like Tampermonkey (Chrome) and Greasemonkey (Firefox).

Chrome also natively accepts insertion of Userscripts, there are details about it in this answer.

Answer 2

You’d have to think of something like this: Let’s say you had a text box, to type something, as a username:

User Name : <input ... value="Nome">

Now, if you typed like this:"onmouseover="event

<input ... value=" "onmouseover="evento ">

Or something like that: We have a text box, type of a browser, if we type such a thing, it can appear "No results found for [searched word]" And if we type: Code, and the browser or other site doesn’t find anything, if you don’t have any security, you can run the script. Let’s say this is HTML code:

<div>Não foi encntrado nenhum resultado para <script>alert("script")</script></div> 

Example 2:

<script type="text/javascript">
function Pesquise(){
/*Script do navegador ou parte de pesquisa de um site*/
document.getElementById("Result").innerHTML  = "Não foi encontrado nenhum resultado para " +  document.getElementById("CaixaPesquisa").value;
}
</script>

<input id="CaixaPesquisa" type="text" value="Código aqui"/><input type="submit" value="Pesquisar" onclick="Pesquise();"/>

<div id="Result">

</div>