Is GMX MailCheck for Firefox safe?
GMX MailCheck for Firefox ships hardcoded OAuth2 client secrets and may silently enable telemetry during version upgrades.
The extension bundles Base64-encoded OAuth2 client credentials for four mail providers (GMX, GMX.com, mail.com, WEB.DE) directly in its publicly inspectable source. When upgrading from versions older than 8.0.0, it force-enables full telemetry collection without prompting the user, and subsequently sends persistent identifiers, account counts, locale, and default-search status to tgw.gmx.net on a daily, weekly, and monthly schedule.
Part of this rating comes from analysis signals we haven't published as detailed findings yet.
Who publishes it1&1 Mail & Media GmbH - no other listings under this identity, 31 shared hostnames
1&1 Mail & Media GmbH - no other listings under this identity, 31 shared hostnames
What this publisher told the store about itself, and the other listings that told it the same thing.
Shared hosts - 31 hostnames
Hostnames hardcoded in this extension that few other listings call. That can mean one operator behind both, and it can equally mean a small shared vendor, so it is context rather than a conclusion. Hosts that many listings call are left out: they are services, not connections.
AI-generated. Findings may contain errors. Those marked Verified have been manually reviewed.
Publishers can request a review.
What it can do
Permissions this extension asks for, as declared in version 8.0.18. Asking for a permission is not a finding on its own - it is what the extension can do if it chooses to.
Read and change your data on gmx.net
https://*.gmx.net/*
Act on the current tab, but only after you click the extension
activeTab
See the address and title of every tab you have open
tabs
Store data in your browser
storage
See, disable and uninstall your other extensions, including your security ones
management
Show you desktop notifications
notifications
Add items to the right-click menu
contextMenus
Sign you in with your Google account
identity
Run searches with your default search engine
search
Where it sends data
Destinations our analysis observed GMX MailCheck for Firefox contacting. Sending data somewhere is not a finding on its own - an extension that syncs your settings has to talk to its own server - but it is where your data can go, and who else it goes to.
- oauth2.gmx.com
GMX MailCheck for Firefox sends data to oauth2.gmx.com. 2 other extensions we have analyzed send data here.
- oauth2.gmx.net
GMX MailCheck for Firefox sends data to oauth2.gmx.net. 2 other extensions we have analyzed send data here.
- oauth2.mail.com
GMX MailCheck for Firefox sends data to oauth2.mail.com. 2 other extensions we have analyzed send data here.
- oauth2.web.de
GMX MailCheck for Firefox sends data to oauth2.web.de. 2 other extensions we have analyzed send data here.
- tgw.gmx.net
GMX MailCheck for Firefox sends data to tgw.gmx.net. No other extension we have analyzed sends data here.