full-disclosure - [FD] Multiple banks - potential risk of an inconsequent client separation

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Date: Fri, 9 Aug 2019 14:48:15 +0200
From: Tim Schughart <t.schughart@...sec-networks.com>
To: Poyo VL via Fulldisclosure <fulldisclosure@...lists.org>
Subject: [FD] Multiple banks - potential risk of an inconsequent client
	separation

Hello together, 

as many of you already know some german banks are sharing the same hoster. 

Via google dorking it is possible to determine some customers of one of those hosters (Fiducia & GAD IT AG). 

The hoster uses a GET parameter called „bankid“ to identify its customers. 

For example: 
https://mobilebanking.gad.de/inm/mobilgad////ptlweb/WebPortal? <https://mobilebanking.gad.de/inm/mobilgad////ptlweb/WebPortal?bankid=8008>bankid=8008 <https://mobilebanking.gad.de/inm/mobilgad////ptlweb/WebPortal?bankid=8008> 

With help of google dorking „inurl:WebPortal?bankid=„ it is possible to enumerate all banks which host their online banking service at Fiducia & GAD IT AG. 
We checked this via whois on the ip net ranges - where another mistake is done - net name „GAD“ in all whois records. 

Another indicator for a shared environment (at least some shared systems) is changing the banking id shown in the following example:
https://www.apobank.de/ptlweb/WebPortal?bankid=8008 <https://www.apobank.de/ptlweb/WebPortal?bankid=8008> 
changed to:
https://www.apobank.de/ptlweb/WebPortal?bankid=8007 <https://www.apobank.de/ptlweb/WebPortal?bankid=8007> 
redirects to https://www.vr.de/privatkunden.html <https://www.vr.de/privatkunden.html> 

In Germany and the EU it is given by law that you have to separate clients data because, e.g. EU-DSGVO. For banks especially BAFIN audits this, too.  

On the following link you’ll find a cleaned list of dork double results, where are around 85 banks are listed with their bankid. 
https://data.prosec-networks.com/d/7cf20ee4b17e44ccb402/?dl=1 <https://data.prosec-networks.com/d/7cf20ee4b17e44ccb402/?dl=1> 

In our oppinion the separation is not given properly, what do you guys think about this? 

Best regards / Mit freundlichen Grüßen 

Tim Schughart 
CEO / Geschäftsführer  

--
ProSec GmbH
Robert-Koch-Straße 1-9
56751 Polch 

Website: https://www.prosec-networks.com 
Phone: +49 (0)261 450 930 90

Sitz der Gesellschaft / company domiciled in: Polch
Registergericht / registry court: Amtsgericht Koblenz, HRB 26457
Geschäftsführer / chief executive: Tim Schughart
USt-IdNr./ VAT ID: DE321817516

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