# CSS Exfil Protection

> Guard your browser against CSS Exfil attacks! CSS Exfil is a method attackers can use to steal data from web pages using Cascading Style Sheets (CSS). This plugin sanitizes and blocks any CSS rules which may be designed to steal data.

Canonical page: [https://chrome-stats.com/d/css-exfil-protection](https://chrome-stats.com/d/css-exfil-protection)

## Overview

- **ID:** `css-exfil-protection`
- **Platform:** Firefox
- **Type:** Firefox add-on
- **Status:** Available
- **Publisher:** Mike Gualtieri
- **Category:** privacy-security
- **Daily users:** 1,015
- **Weekly downloads:** 11
- **Rating:** 4.76 / 5 (50 ratings)
- **Version:** 1.1.0
- **Last updated:** 2020-08-24
- **First published:** 2018-02-06
- **Size:** 46 KB
- **Data as of:** 2026-09-09
- **Store listing:** [Firefox Add-ons Store](https://addons.mozilla.org/firefox/addon/css-exfil-protection/)
- **Website:** [https://www.mike-gualtieri.com/css-exfil-vulnerability-tester](https://www.mike-gualtieri.com/css-exfil-vulnerability-tester)

## Description

### CSS Exfil Protection

CSS Exfil Protection is a powerful Chrome extension designed to safeguard your browser from CSS Exfiltration attacks. CSS Exfiltration is a technique where attackers use Cascading Style Sheets (CSS) to steal sensitive data from web pages. This extension actively sanitizes and blocks any suspicious CSS rules that might be engineered to exfiltrate data, enhancing your browser's security.

By installing CSS Exfil Protection, users can browse the internet with confidence, knowing that their personal and sensitive information is shielded from stealthy CSS-based data theft attempts. The extension runs seamlessly in the background, providing robust protection without compromising browsing performance.

## Rankings

- #3,260 — Overall
- #22 — protect
- #22 — section
- #54 — ai tech
- #80 — film
- #198 — sheets

## Permissions and access

### Permissions

- `http://*/`
- `https://*/`
- `storage`
- `tabs`

### Content script matches

- `<all_urls>`

## Safety

- **Risk impact:** High risk impact
- **Risk likelihood:** Moderate risk likelihood

### Analysis details

- Allows access to all websites, posing a significant security risk as it can monitor and modify data from any visited site.
- This extension website URL may be invalid

> Some risk analysis details are omitted from this free response. [Upgrade to view the full analysis](https://chrome-stats.com/pricing).

## Review summary

CSS Exfil Protection is valued for its added security and ease of use, helping users protect against CSS-based data leaks. However, several users report conflicts with popular extensions like uBlock Origin and problems accessing certain websites due to lack of whitelist options. While some question the legitimacy of the threat it addresses, others appreciate the developer's responsiveness to issues. Overall, it is considered useful but may require compatibility improvements to avoid disrupting web content and other extensions.

### Pros

- Provides additional browser protection against CSS exfiltration attacks.
- Very easy to use and install.
- Helps users identify if their browser is vulnerable to CSS data leaks.
- Contributed by an engaged developer who follows up with users to address issues.

### Cons

- Conflicts with other extensions that modify or interact with CSS, such as uBlock Origin, causing CSS disruptions.
- Lacks a whitelist feature, making it difficult to avoid blocking legitimate sites.
- Can cause functionality issues on some websites, leading to login problems or inability to access certain services.
- Some users find the extension unnecessary or think the described problem is not widely recognized or tested beyond the author's site.

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Source: [Chrome-Stats](https://chrome-stats.com/d/css-exfil-protection)