Is "CSPBlocker" on Firefox Add-ons Safe to Install?

Jeurissen Apps · firefox · v0.0.5

The goal of this extension is to gain back control over your browser by blocking web features a website doesn't need. For now, it supports these features: Web Fonts This blocks any custom web fonts a website may ask for. It's blocked by adding an additional content-security-policy with font-src set to 'none'. Objects (Java / Flash) This blocks any object a website might try to load. This includes java and flash applets. Again this is achieved with a content-security-policy, by setting object-src to 'none'. Reporting apis This blocks any reporting a website might want to do. This can include netwerk issues, content security policy violations, and more. We achieve this by removing the report-to and content-security-policy-report-only headers from any sub/main frame requests. In addition, any content security policy report gets blocked and never sent to the websites server. Workers This blocks any workers a website may ask for. This can be used to block serviceworkers, which can be used to spam the user with notifications, keep running in the background and more. This is blocked by setting worker-src to 'none' in the content-security-policy header. This extension is still in development. In the future, you will be able to select what features it should or should not be blocking. In addition, further controls will be added so you can control what websites should receive what exceptions.

Risk Assessment

Analyzed
49.45
out of 100
MEDIUM

27 security findings detected across all analyzers

Firefox extension requesting 4 permissions

Severity Breakdown

0
Critical
6
High
21
Medium
0
Low
0
Info

Finding Categories

6
Malware Signatures
19
IoC Indicators

YARA Rules Matched

5 rules(6 hits)
postinstall network communication postinstall file manipulation postinstall system command postinstall file download postinstall crypto operations

Requested Permissions

4 permissions
<all_urls>

Access and modify data on every website you visit

Dangerous
webRequest

Intercept, modify, and block all network requests

High
webRequestBlocking

Block network requests before they complete

High
storage
Low

About This Extension

The goal of this extension is to gain back control over your browser by blocking web features a website doesn't need. For now, it supports these features: <b>Web Fonts</b> This blocks any custom web fonts a website may ask for. It's blocked by adding an additional content-security-policy with font-src set to 'none'. <b>Objects (Java / Flash)</b> This blocks any object a website might try to load. This includes java and flash applets. Again this is achieved with a content-security-policy, by setting object-src to 'none'. <b>Reporting apis</b> This blocks any reporting a website might want to do. This can include netwerk issues, content security policy violations, and more. We achieve this by removing the report-to and content-security-policy-report-only headers from any sub/main frame requests. In addition, any content security policy report gets blocked and never sent to the websites server. <b>Workers</b> This blocks any workers a website may ask for. This can be used to block serviceworkers, which can be used to spam the user with notifications, keep running in the background and more. This is blocked by setting worker-src to 'none' in the content-security-policy header. This extension is still in development. In the future, you will be able to select what features it should or should not be blocking. In addition, further controls will be added so you can control what websites should receive what exceptions.

Detailed Findings

7 total

YARA Rule Matches

5 rules

Indicators of Compromise

Network indicators, suspicious strings, and potential IoCs extracted during analysis

URLs
4
Domains
13
Strings
19

All Indicators · 19

Domain
detected Domain: signingca1.addons.mozilla.org

XIOC detected Domain: signingca1.addons.mozilla.org

extracted_from_files

URL
detected URL: https://apps.jeurissen.co

XIOC detected URL: https://apps.jeurissen.co

extracted_from_files

URL
detected URL: http://www.w3.org/2000/svg

XIOC detected URL: http://www.w3.org/2000/svg

extracted_from_files

URL
detected URL: https://apps.jeurissen.co/

XIOC detected URL: https://apps.jeurissen.co/

extracted_from_files

Hash
detected MD5 Hash: f0376d38d065353fe43f2c7b4f247977

XIOC detected MD5 Hash: f0376d38d065353fe43f2c7b4f247977

extracted_from_files

Domain
detected Domain: date.now

XIOC detected Domain: date.now

extracted_from_files

Domain
detected Domain: www.w3.org

XIOC detected Domain: www.w3.org

extracted_from_files

Domain
detected Domain: t.name

XIOC detected Domain: t.name

extracted_from_files

Domain
detected Domain: e.target

XIOC detected Domain: e.target

extracted_from_files

Domain
detected Domain: e.name

XIOC detected Domain: e.name

extracted_from_files

Other
detected Email: [email protected]

XIOC detected Email: [email protected]

extracted_from_files

URL
detected URL: http://addons.mozilla.org/ca/crl.pem0N

XIOC detected URL: http://addons.mozilla.org/ca/crl.pem0N

extracted_from_files

Domain
detected Domain: mozilla.com

XIOC detected Domain: mozilla.com

extracted_from_files

Domain
detected Domain: addons.mozilla.org

XIOC detected Domain: addons.mozilla.org

extracted_from_files

Domain
detected Domain: content-signature.mozilla.org

XIOC detected Domain: content-signature.mozilla.org

extracted_from_files

Domain
detected Domain: carlosjeurissen.com

XIOC detected Domain: carlosjeurissen.com

extracted_from_files

Domain
detected Domain: t7aca1a5c836d2e740723531095377a59.f0376d38d065353fe43f2c7b4f247977.addons.mozilla.org

XIOC detected Domain: t7aca1a5c836d2e740723531095377a59.f0376d38d065353fe43f2c7b4f247977.addons.mozilla.org

extracted_from_files

Domain
detected Domain: window.open

XIOC detected Domain: window.open

extracted_from_files

Domain
detected Domain: apps.jeurissen.co

XIOC detected Domain: apps.jeurissen.co

extracted_from_files

Security Analysis Summary

Security Analysis Overview

CSPBlocker is a Firefox Add-ons extension published by Jeurissen Apps. Version 0.0.5 has been analyzed by the Risky Plugins security platform, receiving a risk score of 49.45/100 (MEDIUM risk) based on 27 security findings.

Risk Assessment

This extension presents moderate security risk. Several findings were detected that may warrant attention. Users should carefully review the permissions and findings before installation.

Findings Breakdown

  • High: 6 finding(s)
  • Medium: 21 finding(s)

What Was Analyzed

The security assessment covers multiple analysis categories:

  • Malware Detection: YARA rule matching against 2,400+ malware signatures
  • Secret Detection: Scanning for exposed API keys, tokens, and credentials
  • Static Analysis: Code-level security analysis for common vulnerability patterns
  • Network Analysis: Detection of suspicious network communications and endpoints
  • Obfuscation Detection: Identification of code obfuscation techniques

Developer Information

CSPBlocker is published by Jeurissen Apps on the Firefox Add-ons marketplace. The extension has approximately 33 users.

Recommendation

Exercise caution with this extension. Review the detailed findings and ensure the requested permissions align with the extension's stated functionality before installation.

Frequently Asked Questions