User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0

Steps to reproduce:

let page = chrome.runtime.getURL("page.html");
page += "&u="+ encodeURIComponent("
https://developer.chrome.com/extensions/tabs#type-MutedInfoReason");

chrome.tabs.update(id, { url: page });

Actual results:

Why is decode the url parameter ?

From: https%3A%2F%2Fdeveloper.chrome.com%2Fextensions%2Ftabs%23type-MutedInfoReason
Is: https%3A//developer.chrome.com/extensions/tabs%23type-MutedInfoReason

This is not happend in Google Chrome.

Hi @Andronachi Marian, first we need some clarifications:

1. The encodeURIComponent() function encodes a Uniform Resource Identifier (URI) component by replacing each instance of certain characters by one, two, three, or four escape sequences representing the UTF-8 encoding of the character (will only be four escape sequences for characters composed of two "surrogate" characters).
2. You provide a URL at steps to reproduce and on at "Actual results" there are two URL encoded. Those are the results after invoking the URL ?
3. I've tried the link provided at steps to reproduce in: https://meyerweb.com/eric/tools/dencoder/ => pressing the "Encode" button the results was (https%3A%2F%2Fdeveloper.chrome.com%2Fextensions%2Ftabs%23type-MutedInfoReason) and pressing the "Decode" button was (https://developer.chrome.com/extensions/tabs#type-MutedInfoReason).
4. So, what is your error?
5. Please make the things clear and let me known after. Thanks for your contribution.

When you pass an EncodedURL to chrome.tabs.update(); or maybe when pressing a URL. The URL in the TAB_BAR will decode automatically all characters %2F to /. How the first post is From -> To.

Why the TAB_BAR URL is decoding automatically the %2F to / ?

Can you provide some clear steps to reproduce that actually work in Firefox?

chrome.runtime.getURL is not something that works when I paste it into the devtools console.
Is this for an addon?

Please be very clear and explicit with every step we need to take to reproduce the bug.

Yes is from addon.

In that case moving to the Webextensions component. I hope they have enough info to reproduce.

https://drive.google.com/file/d/1kdSyA1vQax2wQSvGkLfxzdhwzFiWV-hA/view?usp=sharing

We decode some characters for readability when we display URLs in the location bar, but underneath we still load them fully encoded.

Is not only in the location bar. If i say in DevTools "window.location.href". It's decoded.
Yes is a good idea. But its change the URL from window.location.href. In this case is not a good idea.

If i want to compare a URL and a cache URL i cant because is different from the first time.

(In reply to Andronachi Marian from comment #8)

Is not only in the location bar. If i say in DevTools "window.location.href". It's decoded.

Huh. That's interesting. I don't know what layer that's happening in, then. We pass the URL with entities intact to linkedBrowser.loadURI.

I contacted the reporter and I think I finally figured out what the problem is.

STR:
Install https://addons.mozilla.org/en-US/firefox/addon/holddingtab/
Either drag a bookmark into the URL bar, or drag one of the top sites from the about:newtab page into the URL bar.
The extension will take you to something that looks like: moz-extension://a7d1572e-3beb-4d93-a920-c408fa09e8ea/_source/holding.html?t=news.ycombinator.com&i=icons/holding.png&u=https%3A//news.ycombinator.com/
You'll notice that the u= has unescaped slashes

This can be more easily reproduced as:

var url = new URL("moz-extension://a7d1572e-3beb-4d93-a920-c408fa09e8ea/_source/holding.html?u=https%3A%2F%2Fnews.ycombinator.com%2F");
console.log(url.href); // moz-extension://a7d1572e-3beb-4d93-a920-c408fa09e8ea/_source/holding.html?u=https%3A//news.ycombinator.com/

// but you can do this:
url.search="u=https%3A%2F%2Fnews.ycombinator.com%2F";
console.log(url.href); // moz-extension://a7d1572e-3beb-4d93-a920-c408fa09e8ea/_source/holding.html?u=https%3A%2F%2Fnews.ycombinator.com%2F

Since the SubstitutingProtocolHandler is also extended by nsResProtocolHandler, this change would also apply to resource:// URLs.

Depends on D30344

https://hg.mozilla.org/mozilla-central/rev/948aaa76cfe9
https://hg.mozilla.org/mozilla-central/rev/18861619a4b3