Firefox has long had a feature to protect users from over-aggressive Javascript websites that would generate repeated pop-ups to trick or annoy visitors. Is there a way to disable this protection on specific websites, rather than disabling it entirely?

I've found a way of doing the latter and while it's been years since I've seen one of those popup-bait websites I'd rather not risk my browser's security or stability by disabling the warning globally.

While I understand that any legitimate website has no business abusing pop-ups in this fashion, the ERP portal that I need to use introduced this amazing pop-up feature in a recent update.

Note: this question is about disabling the warning from the user-side.

  • As an aside, in Chrome (where one does not get an overlay, but a truly modal dialog) this could sort of hijack one's full browser. But even then some trickery can help to get out of it, like knowing what window to focus, to enable the proper Close menus or by simply typing a different URL in the location bar. The URL trick also works in Firefox on a Mac, and no trickery is needed to access the Firefox menus. – Arjan Aug 14 '14 at 7:57
  • A related question can be found on StackOverflow which examines Firefox' behaviour in more detail. – Lilienthal Aug 4 '15 at 10:20

This behaviour can be controlled by setting the config parameter dom.successive_dialog_time_limit. This integer value represents a time window in seconds since the last pop-up. If a website generates a new pop-up within that window, Firefox will instead trigger the "Prevent..." dialog.

To set this value:

  1. Copy this string to your clipboard: dom.successive_dialog_time_limit
  2. In FireFox Address bar Enter: about:config and press enter.
  3. Accept the warning dialog.
  4. In the preferences area right-click.
  5. Select New-> Integer
  6. Paste the string you copied previous and click OK
  7. Enter the integer 0 in the next dialog box and click OK.1
  8. Close the about:config page.

1: for most cases, setting this value to 1 or 2 seconds will be sufficient to allow pop-up heavy websites to work without interruption while still stopping malicious infinite pop-up JavaScript code.

  • Accepting this since it seems to work. There's an obvious security/annoyance risk with disabling this of course. From a related question's answer it seems like the popup dialog is shown if the time that passed since the last website popup is smaller than this value. Setting it to 1 would presumably work for the majority of cases while still blocking malicous javascript. – Lilienthal Aug 4 '15 at 10:09

Try this

if (confirm("Do stuff?")) 

Take a look at the noscript firefox extension. By default all js is disabled. You then selectively enable it as and when needed:

The NoScript Firefox extension provides extra protection for Firefox, Seamonkey and other mozilla-based browsers: this free, open source add-on allows JavaScript, Java, Flash and other plugins to be executed only by trusted web sites of your choice (e.g. your online bank).

NoScript also provides the most powerful anti-XSS and anti-Clickjacking protection ever available in a browser.

NoScript's unique whitelist based pre-emptive script blocking approach prevents exploitation of security vulnerabilities (known and even not known yet!) with no loss of functionality...

  • So you'd suggest blanket-disabling the pop-up protection and then only allowing trusted JS to run? That does seem like a valid solution. Personally, I ended up removing NoScript due to the amount of configuration involved in getting new sites to function properly so I'd likely prefer the inconvenience of ignoring security dialogs over that. – Lilienthal Aug 14 '14 at 12:19

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