run-a-script

Name: run-a-script
Rating: 5 (4 reviews)
Author: mivanchev

A minimalistic Firefox extension that allows you to define one JS script which is injected into every page you visit. The addon's code is only a couple of lines long so you can easily verify what's going on.

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Features & Capabilities

A Firefox extension that allows you to define exactly one JS script and inject it into every web page you visit. It uses Firefox' userScripts feature which sandboxes JS code before execution. You should be safe from even the most malicious of actors out there. For at least some convenience, jQuery is injected as well and usable from your script. The code of the extension is deliberately minimal, you are encouraged to review it for security before running the extension.

run-a-script is meant for people with trust issues. There are plenty of extensions out there that you could easily re-implement with a small JS snippet instead of installing. Also useful with uBlock Origin for defeating aggressive sites.

The plugin supports:

sandboxed injection of 1 script + jQuery into all pages, you need to refresh the opened ones
enabling / disabling the script

The plugin does NOT support:

Android – but working on it
Chrome – the whole idea of this extension is to be secure but that's irrelevant if your browser is a black box
saving to and loading from a file – saving would be useful but currently not possible due to a Firefox bug

See the homepage for a usage example.

User Growth & Download Statistics

Add-on

By:

Daily users:

Rating:

Version:

1.0.2 Last updated: 2023-11-25

Version code:

5655860

Creation date:

2022-03-22

Risk:

Permissions:

storage
<all_urls>

Size:

62.19KB

Full description:

Source:

Firefox Add-ons Store

Data ingested on:

2026-06-15

Compare stats and ranking:

Ranking

# 10,045 ▼ 34

Other rankings

#14 in script keyword 28 #32 in jquery keyword 18 ▼ 1#99 in inject keyword 14 ▼ 1#101 in define keyword 11 ▲ 2#137 in scrape keyword 54 ▲ 1

For Developers

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Contact the developer

Chrome-Stats does not own this Firefox add-on. Please use these information below to contact the Firefox add-on developer.

Developed by:

mivanchev

Firefox Add-ons Store

https://addons.mozilla.org/firefox/addon/run-a-script/

User Reviews

by *****, 2025-06-10

by Fi*****, 2024-09-16

jQuery for the motherfuckin win

by Ho*****, 2023-12-17

View all user reviews ›

Is run-a-script Safe?

Risk impact

Risk impact measures the level of extra permissions an extension has access to. A low risk impact extension cannot do much harms, whereas a high risk impact extension can do a lot of damage like stealing your password, bypassing your security settings, and accessing your personal data. High risk impact extensions are not necessarily malicious. However, if they do turn malicious, they can be very harmful.

run-a-script requires a few sensitive permissions. Exercise caution before installing.

Risk impact analysis details

Critical Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.

Risk likelihood

Risk likelihood measures the probability that a Firefox add-on may turn malicious. This is determined by the publisher and the Firefox add-on reputation on Firefox Add-ons Store, the amount of time the Firefox add-on has been around, and other signals about the Firefox add-on. Our algorithms are not perfect, and are subject to change as we discover new ways to detect malicious extensions. We recommend that you always exercise caution when installing a Firefox add-on.

run-a-script has earned a fairly good reputation and likely can be trusted.

Risk likelihood analysis details

High This extension has low user count. Unpopular extensions may not be stable or safe.
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