Microsoft Entra Application Proxy (Azure AD Application Proxy) randomly deletes characters and corrupts web page when viewed through proxy

Zieminek, Tara 10

We are encountering an issue that seems similar to this page with Microsoft Entra Application Proxy (a.k.a. Azure AD Application Proxy). When accessing a web page through the proxy, it appears to randomly delete characters, thus corrupting the web page. Sometimes it deletes a space, so it's not noticeable to the end user. Sometimes it deletes part of a tag which may obviously change the appearance and functionality of the web page. Sometimes it deletes another important character that breaks the webpage functionality (even if the appearance remains ok).

https://learn.microsoft.com/en-us/answers/questions/169829/proxy-corrupts-pages

We aren't able to turn off URL translation to resolve the issue.

There's a similar-sounding issue that was patched for IIS URL rewrite. Is there any chance that a similar fix could be applied by Microsoft Developers to the Microsoft Entra Application Proxy / Azure AD Application Proxy?

https://support.microsoft.com/en-us/topic/fix-response-is-corrupted-when-you-configure-an-outgoing-rule-in-url-rewrite-module-2-0-for-iis-7-0-or-iis-7-5-9a94f4eb-d2a3-0ca1-7518-ce1b348d9f0f#articleFooterSupportBridge=communityBridge

Zieminek, Tara 10 Reputation points

2023-11-02T17:08:12.0233333+00:00

I'm suspect this is also affecting many other users who get bugs and don't realize why. I just happened to notice the deleted characters by chance when I was troubleshooting the issue.
Zieminek, Tara 10 Reputation points

2023-11-02T17:08:39.71+00:00

@Alfredo Revilla - Upwork Top Talent | IAM SWE SWA I have created a new question, as suggested.
JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-02T20:42:00.7566667+00:00
@Zieminek, Tara

Thank you for your detailed post!

I understand that you're having issues with the Microsoft Entra Application Proxy when accessing a web page through the proxy, since it looks to be randomly deleting characters and corrupting the web page. To help troubleshoot this issue and ensure this isn't a bug with the service, can you look into the below.

When you published your Application Proxy app, are all your pages accessible when accessing the application / are they under your root path? For example, if you published the path https://yourapp/app, but the application calls images or files in https://yourapp/media, they won't be rendered.

Have you verified if any resources are missing or if you're running into any errors? You can do this through a network trace (such as Fiddler, or F12 tools in Internet Explorer/Microsoft Edge), loading the page, and looking for 404 errors. That indicates the pages currently cannot be found and that you need to publish them.

To gain a better understanding of your issue, can you also share screenshots of what you're seeing keeping in mind PII.

Additional Links:

Troubleshoot Application Proxy problems and error messages

Application page does not display correctly for an Application Proxy application

Links on the page don't work for an Application Proxy application

Understand and solve Microsoft Entra application proxy CORS issues

An Application Proxy application takes too long to load

Troubleshoot networking issues

I hope this helps!

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.
Zieminek, Tara 10 Reputation points

2023-11-03T15:42:06.7366667+00:00
Thank you for the response @JamesTran-MSFT

In response to your comments:

Yes, they are accessible. The issue is either one or two single deleted characters in the page when I compare the "view source" for the page, not a missing resource. Also, we aren't loading much media on the page other than a logo (it's a form). All of the media appears to load without a problem.

No errors are being thrown on the page

In reference to the additional links:

The corruption (deleted character) occurs intermittently and at different spots on the page.

There are no 404 errors.

Links on the page all work

It is not a CORS issue (no CORS errors).

Load time is not the issue

It's not a networking issue; the page loads (just with a deleted character sometimes) and other pages on the Azure AD Application Proxy website load without problems.

Here are some examples of the issue when I "view source" compared to the source of the non-proxied pages. Note that it's also intermittent; the exact same page page may load without the missing character the next day, or with a missing character in a different spot.

Below I have shared some examples of the issue. (Here, I am comparing the proxied version of the page to the non-proxied version of the same page using VS code.) As you can see, sometimes it deletes a space (which doesn't affect the end user), but sometimes it deletes a character that's part of a tag (so that breaks the page).

For example, it changes <input to <nput, <li to <i, <a class to < class, <hr /> to <r />.
JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-06T19:44:12.7433333+00:00
@Zieminek, Tara

I wanted to check in and see if you had any other questions or if you'd like our support team to take a closer look into your issue?

I noticed that your recent experience was not helpful, and to better improve our processes and learn from our customers, I'm eager to know what could have been done better.

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.
JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-09T19:16:01.35+00:00

@Zieminek, Tara

I wanted to check in and see if you had any other questions?

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.

If the information helped address your question, please Accept the answer. This will help us and also improve searchability for others in the community who might be researching similar information.
JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-28T21:23:13.84+00:00

@Zieminek, Tara

I wanted to check in and see if you had any other questions or if you were able to resolve this issue?

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.

If the information helped address your question, please Accept the answer. This will help us and also improve searchability for others in the community who might be researching similar information.
Zieminek, Tara 10 Reputation points

2023-11-28T21:33:54.6566667+00:00

No, unfortunately none of the suggestions helped to resolve the underlying problem with Azure AD App Proxy.
Zieminek, Tara 10 Reputation points

2023-11-29T21:06:28.5533333+00:00

As additional information, this happens on the page even if there are no URLs being rewritten on that particular page, but it didn't happen on our test environment when URL rewrite was turned off. It's definitely a bug caused by the URL rewrite.
JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-12-04T21:03:07.13+00:00
@Zieminek, Tara

Thank you for following up on this and I apologize for the delayed response!

The App Proxy team reached out to me and is aware of this potential bug and they recommended opening a support request. This'll help them take a closer look into your environment, gather the necessary logs, and properly troubleshoot your issue in order to determine the root cause.

If you'd like to work closer with our support team on this, please let me know. I'd be happy to enable a one-time free technical support request for your subscription to get this issue resolved. Note: If you're a CSP Partner, you won't be able to open a support request directly – only the CSP partner has this ability.

I hope this helps!

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.

If the information helped address your question, please Accept the answer. This will help us and also improve searchability for others in the community who might be researching similar information.

1 answer

JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-03T21:46:37.8533333+00:00
@Zieminek, Tara

Thank you for such a detailed post!

I reached out to our Azure AD App Proxy team with your issue details, and I also noticed that you mentioned - you aren't able to turn off link translation to resolve your issue. However, as of right now, the recommended way that may resolve your issue would be to disable link translation.

The App Proxy team also recommended opening a support request so they can work with you to gather more data and logs to better investigate your issue.

If you'd like to work closer with our support team on this, please let me know. I'd be happy to enable a one-time free technical support request for your subscription to get this issue resolved.

Note: If you're a CSP Partner, you won't be able to open a support request directly – only the CSP partner has this ability.

Additional Links:

How link translation works

Does using Link translation affect performance?

Publish applications via Application Proxy - Link Translation

I hope this helps!

If you have any other questions, please let me know. Thank you for your time and patience throughout this issue.

If the information helped address your question, please Accept the answer. This will help us and also improve searchability for others in the community who might be researching similar information.
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JamesTran-MSFT 36,656 Reputation points Microsoft Employee

2023-11-03T22:20:26.3733333+00:00

@Zieminek, Tara

Thank you for again for your time and patience on this issue!

I also shared your feature request with the App Proxy team regarding a similar issue with the IIS URL rewrite.

I noticed that your recent experience was not helpful, and to better improve our processes and learn from our customers, I'm eager to know what could have been done better.

If you have any other questions, please let me know. Thank you!
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Microsoft Entra Application Proxy (Azure AD Application Proxy) randomly deletes characters and corrupts web page when viewed through proxy

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