Safe PDF viewers.

Andy Ful

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Post updated.

Please, do not post about
Adobe Acrobat Reader and PDF viewers in web browsers:
https://malwaretips.com/threads/safe-pdf-viewers.109756/post-955966
Let's also limit our posts to Windows OS.


Many users view PDF documents, but we know that such documents can be dangerous. Most of the popular PDF readers were vulnerable to exploits in the past and some of them were not patched for a year or more because of using free opensource DLLs. This was true even for less known PDF viewers like Sumatra PDF.

So it is reasonable to find a good & super safe PDF reader (especially for casual users). I have one candidate to discuss. It is an application from Microsoft Store: PDF Reader - View, Edit, Annotate by Xodo.

Pros.
  1. It is from Microsoft Store and runs in AppContainer.
  2. It can work under several Exploit Protection mitigations. All Windows mitigations can be applied except ACG, Block untrusted fonts, Disable Win32k system calls, EAF, IAF, and StackPivot.
  3. The application can be protected by strong mitigations like disabling child processes and running only the code signed by Microsoft or Microsoft Store.
  4. Javascript can be enabled/disabled.
  5. It is extremely fast.
  6. It can open safely MS Office documents (*.docx, *.xlsx, *.pptx are converted to PDF) . No active content after conversion to PDF. The conversion does not use the Internet.
Cons.
  1. It is not as trusted and popular as for example Adobe, Foxit, etc.
  2. Not many languages are supported (German, English, French, Italian, Portugal, Spanish, and 3 Asian languages).
  3. It is not possible to block hyperlinks, so after clicking one of them the malicious/compromised website can be opened in the web browser. This can be solved as follows:
    https://malwaretips.com/threads/safe-pdf-viewers.109756/post-956334

The Blog.
https://blog.xodo.com/
About Xodo
https://www.xodo.com/about_us.html
Features.
https://www.xodo.com/#features
 
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Andy Ful

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open PDF with any chrome based browser ( i personally use brave for personal and edge chromium for work)
It is OK, but the Chrome PDF viewer is not as fast. Try to scroll the book or Science magazine in PDF format to see the difference. Furthermore, it is not as safe (by design) as the solution from the OP:
  1. Opening documents in the web browser can end with drive-by downloads or phishing websites (via embedded URLs) - this can be important when protecting happy clicker users. If you use a dedicated PDF viewer, then Internet access can be disabled by the firewall rule.
  2. Chrome is the most popular web browser so its PDF viewer is most targeted for exploits.
  3. If Chrome is not hardened then the PDF exploit can get some valuable information about users' web browsing, etc., even if the exploit is contained in the sandbox.
  4. If the Chrome session is exploited in the sandbox, then it is not safe to open PDF documents that contain personal or confidential information.
Of course, for many users, the built-in PDF viewer in Edge will be enough.
 
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Andy Ful

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I open pdf files in Chrome. It's sandboxed. What else would I want.
PDF documents in Adobe Acrobat Reader are sandboxed too.:)
Many users are very happy with Adobe applications and too many are infected anyway.
But, the problem here is different. It is not related to escaping the sandbox but to the proper isolation of different things that can happen into the sandbox. There is a reason why Microsoft introduced Application Guard for Edge (safe browsing). They did it to isolate safe browsing sessions from normal web browsing.

Of course, for occasional viewing of PDF documents, Edge is OK. Just like using a free AV for security. You have a good chance to avoid malware infection via PDF files.
Anyway, the purpose of this thread is to find something much safer, for people who need it.(y)
 
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Andy Ful

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SpiderWeb,
You probably think about Chromebooks. Opening PDF files in Chrome on Chromebook is much safer compared to Windows. Look at point 1 in my post:
https://malwaretips.com/threads/safe-pdf-viewers.109756/post-955966
Still, there is a possibility to land on a phishing webpage.
Furthermore, there are some differences between implementing Chrome on Chromebook and on Windows. So, some exploits will not work for Chrome on Chromebook.
 
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Andy Ful

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There is one crazy idea about safe PDF viewing. One can use a secondary web browser (Edge or Chrome) only for viewing PDF files and disable Internet access to this web browser (cautious users can keep the Internet alive). Using Edge for that would be slightly more secure because one can force running only the code signed by Microsoft (via Exploit Protection). It is an idea proposed a few years ago by one of the MT members.
 

Telos

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I added the information in OP to skip the PDF viewers in the web browsers.
What about privacy? Does opening a PDF on Edge or Chrome share anything about my use... What if I highlight passages, or make annotations with the browser tools?

I don't think any of us know, and I will err on the side of tinfoil.
 

Vasudev

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I use Xodo on Android or on Windows Phone which worked flawlessly with Dark Accents which was very helpful in reading notes. On Windows, I use sumatraPDF. I think I will into situations where I might need Adobe reader for validating some govt docs that use e-sign which doesn't work on Linux/Windows freewares but only on commercial licenses like master PDF editor or Adobe reader Pro.
 

jogs

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On Android I use Xodo because of its very good search facility, Though I rarely use mobile for any kind of work.
Same way I use PD-XChange on Windows because of its very good search facility as it can search together in all opened files. Even more, it can search multiple words at the same time that too in multiple opened file, this is something that I haven't found on any other software.
 

Andy Ful

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What about privacy? Does opening a PDF on Edge or Chrome share anything about my use... What if I highlight passages, or make annotations with the browser tools?
The idea is to use another web browser for the Internet (also for downloading PDF files) and another for PDF viewing (no Internet). No Internet = No sending private information.
 
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Andy Ful

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I have tried to use the Privexec tool to run Sumatra PDF in AppContainer. It can be done, but not especially convenient. I did not found out yet how to add access to selected folders in Privexec. I have to learn something more about appxmanifest.xml content.
 
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