Category Archives: Tips

It is not a vulnerability. It is a feature. A Zendesk customer? Act now!

Data Leakage, Government and Regulation, Privacy, Tips, Vulnerabilities, What have I discovered?Eitan Caspi

I am not a Zendesk expert but I have seen enough. Here is my story.

The short version:

If in your ZD settings the check box of “Require authentication to download” (in the site path of Admin > Settings > Tickets) is NOT selected (hence Disabled) – there are web address/URLs at sub-domain sites of zdusercontent.com that store files that are accessible without any authentication, anonymously, and they can be files that hold private data of your customers.

This check box is disabled by default! By a ZD intentional decision. Customers of ZD may not even know that and not change this default and thus the files will remain accessible anonymously. Not nice. I guess not GDPR compliant.

ZD support article about this check box – https://support.zendesk.com/hc/en-us/articles/203927716-Attachments-in-Zendesk-Support#sec5

Some of this data is indexed by Google, sample searches:

site:zdusercontent.com

https://www.google.co.il/search?q=site%3Azdusercontent.com

site:zdusercontent.com receipt

https://www.google.co.il/search?&q=site%3Azdusercontent.com+receipt

And so on – try the words like bank , “credit card”

Also, if you go to the following link you can find who ZD customers are

https://www.zendesk.com/why-zendesk/customers/

And then you can search by their names, Say, Uber

site:zdusercontent.com uber

https://www.google.co.il/search?q=site:zdusercontent.com+uber

These URLs are quite long and use complex and random characters, so they are not easy at all to guess. But, they can be sent to your customers from the ZD system as links in emails (which can be exposed in many ways) or they can be logged in your security systems, hence exposed to your IT team (see the longer version of this story below).

Since these URLs are accessed anonymously, I guess the only possible way to track who used them is by source IP, which of course can easily not be the real IP of the person who initiated this access (say if the person is using a proxy server or public VPN service).

So, my recommendation to you is to enable this check box, which will change this behavior and any access to any attachment file will force the accessing person to first be authenticated by the ZD system.

This may have negative operational results for the ease of your customers’ access to these files – so weight the pros and cons before doing this change.

The long story:

One day last week, as I was reviewing our gateway alerts, I noticed a strange link, beginning with a sub-domain of zdusercontent.com and followed by medium size string of a URL parameter. I searched to find who is the owner of this domain and found it is owned by ZD. Cool. Safe. I clicked it.

A JPG file loaded into my browser. It was a photo a customer of ours took, to prove his identity, a personal identification document… whoaaa… what???

Although I knew I didn’t log into ZD recently, I cleared my browser’s cache and all cookies, and tried again. The same…

I tried using another browser. The same.

I tried from another PC inside the company. The same.

I tried from my private mobile phone, I tried from my home. All the same.

I tried another link found for this domain – a zip file with multiple files sent by another customer. Not nice, not at all.

Woooo, I said to myself, we’re going to make tons of money on this one via a bug bounty. Zero authentication for customers’ private data. No joke.

So, I found ZD bug bounty page at HackerOne – https://hackerone.com/zendesk

It didn’t mention that the domain of zdusercontent.com is included in the bounty program.

I didn’t give up – I asked HackerOne about it, but quickly I learned HO is not really responsive nor knowledgeable so I turned directly to ZD security.

They promised me that zdusercontent.com is included in the bounty and that they wish to accept my report. (BTW, even now this domain is not mentioned as eligible to their above bug bounty page).

So I PGPed my findings and sent it to ZD, including an offer to simply block search engines from indexing these sites with a simple robots.txt file.

They replied:

”

To summarize the issue you reported to us, you found files (Zendesk ticket attachments) were indexed by the Google search engine and could be accessed publicly, without authentication, and in some instances without the token parameter in the URL. If I have missed anything please correct me.

This specific topic is something which has been brought to our attention before and has been discussed internally. I want to assure you everything is currently working as intended. All Zendesk accounts have an admin setting to require authentication to view/download a ticket attachment: https://support.zendesk.com/hc/en-us/articles/203927716-Attachments-in-Zendesk-Support#sec5. If you are worried about potential information disclosure please enable that setting to restrict access to all ticket attachments, including the files which are indexed by search engines. In that page you can see the only time ticket attachments are indexed by search engines is when the links are posted on third-party public websites. The files being indexed are not being leaked from Zendesk, but intentionally posted to public locations. This setting exists because the feature of publicly shareable ticket attachments are a popular request from our customers. That being said, I completely agree with you that there is no reason to not include a robots.txt file for that domain. There is currently an open request to implement robots.txt on a few domains which handle customer attachments which should be rolled out by the end of the year, if not much sooner.

In the meantime, if enabling the “require authentication” for attachments doesn’t fit your organization’s needs, please take a look at our Attachments API which would allow you to handle attachments on an individual basis. You can redact comment attachments via the information provided here: https://developer.zendesk.com/rest_api/docs/core/attachments#redact-comment-attachment. You can permanently delete uploads via there information provided here: https://developer.zendesk.com/rest_api/docs/core/attachments#delete-upload.

”

And their next response after I replied to the above with amazement to their answer and asking if this check box is disabled by default:

”

The administrative setting of “Require authentication to download” is disabled by default. Many of our customers specifically ask for the ability to host and share non-sensitive documents with their customers so we give them the ability to configure their account to best fit their needs. Additionally, many of our customers’ customers utilize Zendesk strictly through e-mail and not the actual Zendesk UI, therefore they wouldn’t have a registered account to begin with which could cause a lot of confusion if the e-mail correspondence contains attachments. That being said, I’ve escalated this to my manager to start the discussion with our Product teams regarding the default nature of that setting. I can’t promise a change as this may be an accepted risk using the shared responsibility model.

I’ve already mentioned the API endpoints available which Zendesk accounts can use to redact/delete all non-inline attachments. If you are worried about any specific attachments I would reach out to that specific account and address the issue with them. If they are unsure how to proceed with that type of request Zendesk is more than happy to walk them through that process.

”

I think ZD is making a mistake by disabling this check box by default, loading on itself the legal responsibility for data exposure, when some of it may be private.

If they enabled it by default – they would have been covered themselves better, making the default more secure and if customers would try to change it – they would be displayed with a flashing bold warning about the consequences of such change, and if they do change it – they will be the ones responsible for any relevant data exposure.

So, there goes my imaginary pile of bug bounty money, but as least I came across a good story and a chance to let you know about this risk and possibly mitigate it.

A next day addition I forgot to add – I found only one place on the web that already related to this issue – and it is from a poker forum, where a customer complaints about his personal data being freely exposed on the web, in a zdusercontent.com sub-domain. And he is furious… – https://forumserver.twoplustwo.com/252/global-poker/security-issue-personal-documents-posted-open-web-1715425/

(4-May-2020 – I added here the above forum discussion as a PDF file, for archiving – zd-angry-customer)

Addition at 22-Nov-18: Hi Zendesk folks, I see you reacted quickly and cleared the search results from Google. That’s very good. Just remember there are more search engines you need to handle, some main ones:

Bing – https://www.bing.com/search?q=site%3Azdusercontent.com

Yahoo – https://search.yahoo.com/search;?fr2=sb-top-search&p=site%3Azdusercontent.com

DuckDuckGo – https://duckduckgo.com/?q=site%3Azdusercontent.com&t=h_&ia=web

And I’m sure you will find more.

Windows Update reset script

Patching, Tips, ToolsEitan Caspi 
There are quite a few times that Windows Update gets stuck with bizarre error codes.
At first I tried Microsoft Windows Update Troubleshooter, but it did not help in most of
the cases.
.
There are various sites that suggest a manual, long and tedious process to reset 
Windows Update, but better yet - there is a script which automates this process, 
so with only a few keystrokes it runs this process properly, fast and easy. This 
script certainly helped me, so I guess it will help you too. Give it a try.

How to protect yourself from the Samsung keyboard vulnerability in Android devices

Application Security, Hardening and Mitigations, Tips, Vulnerabilities, What have I discovered?Eitan Caspi

A few weeks ago, on June 2015, the mobile devices security company “NowSecure”, has published a post about a vulnerability they have found, titled “Remote Code Execution as System User on Samsung Phones Summary”, discovered by its researcher, Mr. Ryan Welton.
This research was also marked using two official vulnerability identifications of CVE-2015-4640 and CVE-2015-4641.

On the above blog post the company wrote “Unfortunately, the flawed keyboard app can’t be uninstalled or disabled”.
I believe this is not fully correct as the relevant Android service of the this keyboard can be disabled if the device is rooted.

In the rest of this post I will show you how to do just that.

***
Disclaimer:
Following are the steps of how to work-around the vulnerabilities mentioned in the post blog of “NowSecure” – but the fact it worked for me does not necessarily means it will work for you or that it won’t harm your device and/or data.
I will have NO responsibility NOR liability for the following steps, if you will perform the following steps – it will be on your own personal responsibility and liability.
***

There is a workaround, which means it is not fixing the problem and the relevant software is still vulnerable, it is just that we will make sure the relevant software will not load into the device memory, so attackers will not be able to exploit this vulnerability.

***
The following procedure requires a root access for the device.
***

The concept outline is:
1. Installing another Android keyboard software
2. Making the new keyboard app the device active keyboard
3. Disabling the Samsung keyboard (including across device reboots)

This replaces the vulnerable keyboard with a (probably…) non-vulnerable keyboard and blocking the vulnerable keyboard from loading into memory, so it cannot be exploited.

First of all – make a full backup of the target Android device! And save the backup output OUTSIDE the device itself!

1. Make sure you have a root access on your Android device.
The free app of “Root Checker” may help you verify this.
If you do not have root access – the decision if and how to get root access is up to you to decide as it has many and serious implication on your device operation, maybe even its warranty – further beyond this workaround.
See the following two articles discussing the advantages and disadvantage of rooting and Android device:
a. Rooted vs. Unrooted Android: Your Best Arguments
b. To Root or Not to Root

2. Install an alternate free keyboard, like the “Google Keyboard”.
Here are some recommendations (not by me) for other alternate keyboards apps.

3. Make the non-Samsung keyboard the active system keyboard
The steps to do this may change from Android version to another, but you can get a hint in the following articles:
a. How to replace your Android or iOS keyboard
b. Type in style: How to change your Android keyboard

4. Reboot the device and make sure that the new keyboard app is the active keyboard and that it is working properly (say, do a Google search)

5. Install the free app of “Disable Service”. I installed and used it and it worked fine for me.

6. Disable the “Samsung Keyboard” app using the following steps:
a. Open the “Disable Service” app and choose the “System” tab on the right side of the app interface
b. Find the app named “Samsung Keyboard” (the actual name (partial or complete) of the app may be different as it may be written using the interface language of your phone) and choose it
(you can easily find the “Samsung Keyboard” app using the “Disable Service” app search option (the magnifier icon at the top-left side of its interface) – just type there “samsung”)
c. Un-check all the check boxes of the sub-items listed, the ones which the “Samsung Keyboard” is attached to. Once you un-check an item it will be disabled and its text color will turn from white to red.
You will probably be prompted, using a pop-up window, to grant the “Disable Service” app a root access – you HAVE to approve this request for this procedure to succeed (the pop-up window will enable you to limit this access for only 15 minutes. You can do this as well, as you suppose to complete the whole procedure within a few minutes)
d. That’s it – exit the app
e. To verify that the “Samsung Keyboard” is disabled – return to the Android keyboard selection section, as mentioned in step number 3 above and make sure that there is no item of “Samsung Keyboard” listed

In case you wish to re-enable the Samsung keyboard, use the following steps:

a. Open the “Disable Service” app and choose the “System” tab on the right side of the app interface
b. Find the app named “Samsung Keyboard” (the actual name (partial or complete) of the app may be different as it may be written using the interface language of your phone) and choose it
(you can easily find the “Samsung Keyboard” app using the “Disable Service” app search option (the magnifier icon at the top-left side of its interface) – just type there “samsung”)
c. Check/Select all the check boxes at the list you will be presented with. Once you check/select an item it will be enabled and its text color will turn from red to white.
You will probably be prompted, using a pop-up window, to grant the “Disable Service” app a root access – you HAVE to approve this request for this procedure to succeed (the pop-up window will enable you to limit this access for only 15 minutes. You can do this as well, as you suppose to complete this procedure within a few minutes)
d. Exit the app
e. To verify that the “Samsung Keyboard” is enabled – return to the Android keyboard selection section, as mentioned in step number 3 above and make sure that an item of “Samsung Keyboard” is listed there

The above procedure is meant for most folks as it easy and less prone to cause any harm – most folks should use it.

The following procedure will give the same result but it is intended for more technically experienced folks as it is more prone for possible mistakes and damage, as it is using low-level operating system commands. Use it only if are very technically knowledgeable about the low-system-levels of Android.

Perform steps 1 to 4 the same as mentioned above.
From step 5 and forward use the following steps:

5. Install a shell/terminal emulator like the free app of “Terminal Emulator for Android”, which I tested and found it to work fine and easy.

a. Open the “Terminal Emulator for Android” app and at the command line type the text “su” (without the quotes. su means “super user”, which is what we call “root” mode) and hit the “Enter” key, found on the edge of the lower-right corner of the app’s online keyboard. It looks like a thin line with large arrow-head that is pointing to the left
b. You will probably be prompted, using a pop-up window, to grant the “Terminal Emulator for Android” app a root access – you HAVE to approve this request for this procedure to succeed (the pop-up window will enable you to limit this access for only 15 minutes, you can do this as well, as you suppose to complete this procedure within a few minutes)
c. You will be returned to the command line. Notice that the sign at the right side of the line’s initials is changed from the dollar sign, “$”, to be the sign of “#”, which symbols you are now in “root” mode.

***Be very careful here as you can make real damage using the root mode***

d. Type the following line exactly, and once you completed writing it – press the “Enter” key:
pm disable com.sec.android.inputmethod

If all is fine you will be replied with a message of:
Package com.sec.android.inputmethod new state: disabled

e. Exit the app by clicking on the “X” sign on the app’s upper-right corner

To enable back the Samsung keyboard using the same app:

Do most of the same steps as mentioned above using the “Terminal Emulator for Android” app, but for step “d” change the command to be:
d. Type the following line exactly, and once you completed writing it – press the “Enter” key:
pm enable com.sec.android.inputmethod

If all is fine you will be replied with a message of:
Package com.sec.android.inputmethod new state: enabled

e. Exit the app by clicking on the “X” sign on the app’s upper-right corner

.

That is all. I hope this post will assist you in protecting yourselves from this vulnerability.

Cheers!

Eitan Caspi

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