Is "WEB.DE MailCheck for Firefox" on Firefox Add-ons Safe to Install?

1&1 Mail & Media GmbH · firefox · v8.0.18

E-Mail notification in the browser and on the desktop Read and write your emails with only one click Access to all your email accounts in only one tool (e.g. WEB.DE , GMX , 1&1 , mail.com and many more) Encrypted SSL connection and password protection with highest security standards Optional: Access your emails via mail icon on start page

Risk Assessment

Analyzed
100
out of 100
CRITICAL

183 security findings detected across all analyzers

Firefox extension requesting 37 permissions

Severity Breakdown

0
Critical
90
High
93
Medium
0
Low
0
Info

Finding Categories

90
Malware Signatures
10
Obfuscation
82
Network

YARA Rules Matched

14 rules(90 hits)
credential env files postinstall network communication postinstall system command postinstall file manipulation postinstall obfuscation postinstall registry modification NoUseWeakRandom postinstall crypto operations postinstall file download postinstall persistence mechanism OriginsNotVerified LocalStorageShouldNotBeUsed postinstall environment access UntrustedContentShouldNotBeIncluded

Requested Permissions

37 permissions
management

Manage other installed extensions

Dangerous
<all_urls>

Access and modify data on every website you visit

Dangerous
identity

Access your identity and sign-in tokens

High
activeTab
Medium
tabs
Medium
storage
Low
notifications
Low
contextMenus
Low
search
Low
https://*.web.de/*
Low
https://*.gmx.net/*
Low
https://*.gmx.de/*
Low
https://*.gmx.ch/*
Low
https://*.gmx.at/*
Low
https://*.gmx.com/*
Low
https://*.mail.com/*
Low
https://*.1und1.de/*
Low
https://*.1and1.com/*
Low
https://suche.web.de/*
Low
https://dl.web.de/backend/post.html
Low
https://dl.gmx.net/backend/post.html
Low
https://dl.gmx.com/backend/post.html
Low
https://dl.mail.com/backend/post.html
Low
https://dl.1und1.de/backend/post.html
Low
https://www.adsensecustomsearchads.com/afs/ads?*
Low
https://www.adsensecustomsearchads.com/afs/ads/*
Low
https://1und1.de/login/oauth2/*
Low
https://www.1und1.de/login/oauth2/*
Low
https://gmx.net/login/oauth2/*
Low
https://www.gmx.net/login/oauth2/*
Low
https://gmx.com/login/oauth2/*
Low
https://www.gmx.com/login/oauth2/*
Low
https://mail.com/login/oauth2/*
Low
https://www.mail.com/login/oauth2/*
Low
https://web.de/login/oauth2/*
Low
https://www.web.de/login/oauth2/*
Low
https://login.live.com/*
Low

About This Extension

<ul><li>E-Mail notification in the browser and on the desktop</li><li>Read and write your emails with only one click</li><li>Access to all your email accounts in only one tool (e.g. <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/5cff19bdb0c5a157dcbcf3f3f022cbc4794fa85e6eec5f3aeab7fc39e005f70f/http%3A//WEB.DE" rel="nofollow">WEB.DE</a>, <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/4c7bb370b79facbf09837132859273528fde29d215eccd9a0a87480737e1e3ab/http%3A//gmx.net/" rel="nofollow">GMX</a>,<a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/97a21e25e1265f1a1578520cd11b3ad83ff65d14915e70e89e399f67940b6a26/http%3A//home.1und1.de/" rel="nofollow">1&amp;1</a>, <a href="https://prod.outgoing.prod.webservices.mozgcp.net/v1/6b59bf8b94224a366968d483216df0e725c9c203992ca62f2fd4a4f66ebeeb53/http%3A//mail.com" rel="nofollow">mail.com</a> and many more)</li><li>Encrypted SSL connection and password protection with highest security standards</li><li>Optional: Access your emails via mail icon on start page</li></ul>

Detailed Findings

183 total

YARA Rule Matches

14 rules

Security Analysis Summary

Security Analysis Overview

WEB.DE MailCheck for Firefox is a Firefox Add-ons extension published by 1&1 Mail & Media GmbH. Version 8.0.18 has been analyzed by the Risky Plugins security platform, receiving a risk score of 100/100 (CRITICAL risk) based on 183 security findings.

Risk Assessment

This extension presents critical security risk. Severe issues were detected, potentially including malware indicators, exposed secrets, or dangerous behaviors. Installation is strongly discouraged until these issues are addressed.

Findings Breakdown

  • High: 90 finding(s)
  • Medium: 93 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

WEB.DE MailCheck for Firefox is published by 1&1 Mail & Media GmbH on the Firefox Add-ons marketplace. The extension has approximately 22K users.

Recommendation

This extension is not recommended for installation without thorough manual review. Consider alternatives with lower risk scores, or contact the developer to address the identified security concerns.

Frequently Asked Questions

Similar Extensions

Related extensions from the same publisher or marketplace

mail.com MailCheck

1&1 Mail & Media GmbH

CRITICAL 1K users

GMX MailCheck for Firefox

1&1 Mail & Media GmbH

CRITICAL 17K users

GMX MailCheck for Firefox

1&1 Mail & Media GmbH

CRITICAL 18K users

WEB.DE MailCheck for Firefox

1&1 Mail & Media GmbH

CRITICAL 23K users

mail.com MailCheck

Unknown Developer

CRITICAL

mail.com MailCheck

1&1 Mail & Media GmbH

CRITICAL 1K users