Linked Questions

8 votes
3 answers

How to safely allow upload of executable files [duplicate]

I need help regarding file uploading. In one of my projects the client wants to allow a file upload without restrictions on the file type. But I'm afraid that then users can upload executable files ...
Ravi's user avatar
  • 89
1 vote
1 answer

How can I make sure an image uploaded to my server is not harmful? [duplicate]

I would like to allow users of my app to upload images in different formats that other users can view (including webm videos). But I would also like to make sure that the images are actual images and ...
user2741831's user avatar
52 votes
4 answers

How to inject executable, malicious code into PDF, JPEG, MP3, etc.?

I wanted to know if its generally possible to inject executable code into files like PDFs or JPEGs etc., or must there be some kind of security hole in the application? And if so, how would one do ...
JohnnyFromBF's user avatar
  • 1,413
25 votes
4 answers

What is the corrupted image vulnerability? How does it work?

What exactly happens when someone injects malicious binary code into an image file (on Windows)? How is that done?
Moshe's user avatar
  • 1,851
20 votes
3 answers

Does X-Content-Type-Options really prevent content sniffing attacks?

In Tangled Web Michal Zalewski says: Refrain from using Content-Type: application/octet-stream and use application/binary instead, especially for unknown document types. Refrain from returning ...
Andrei Botalov's user avatar
26 votes
3 answers

What steps should be taken to validate user uploaded images within an application?

Recently I have worked on a number of applications that need to process user uploaded images steps have been taken to validate the extension and the mime type. But what else can be done to ensure ...
Mark Davidson's user avatar
17 votes
3 answers

Using file extension and MIME type (as output by file -i -b) combination to determine unsafe files?

We allow users to upload a number of files, all of which we either send over to scribd (doc, xls, ppts, etc) or display as a video ourselves (flv, mov, mp4, etc in flowplayer). To avoid users ...
siliconpi's user avatar
  • 1,087
14 votes
3 answers

Is it possible to inject HTML into image to provoke XSS?

Some answers mention that it's possible to inject attacker-controlled HTML into images and therefore provoke XSS. I guess that this HTML will be processed by browser only if hole exists in browser. ...
Andrei Botalov's user avatar
8 votes
5 answers

How should I serve untrusted / unsanitized documents (PDF, DOC, XLS) to end users over the web?

My website will be hosting documents for end users and I would like to make this as secure as possible. Question Assuming that I have a need to share documents on a website that may contain hostile ...
makerofthings7's user avatar
9 votes
2 answers

C# Image.FromStream is that secure?

after reading the data from the request as Stream i needed to convert it to Image so i used this Method: Stream inputStream = HttpContext.Current.Request.InputStream; Image img = Image.FromStream(...
Yaniv's user avatar
  • 191
2 votes
4 answers

Security risks of hosting user-supplied images?

I have a program that will accept and fetch images from urls. It will check if the extension is .png, .jpg, etc... I will fetch these files and store them, they will be shown to users in a gallery (...
Lucas Kauffman's user avatar
5 votes
5 answers

Should there be an anti-virus used on client provided files?

This is based on Stack Exchange podcast # 25. I really don't understand why there would need to be virus checking on uploaded files. It would generally be a bad idea to execute anything which was ...
cwallenpoole's user avatar
2 votes
1 answer

How confident is MIME blacklisting on a proxy server?

We are blacklisting a number of MIME types on our proxy server so users can't download certain file types, for example, executables. Could it be possible that somehow, a malicious server can trick a ...
lithium's user avatar
  • 23