File upload means sending a file from a local system to a remote system such as a server or another client with the intent that the remote system should store a copy of the file being transferred.

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34
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5answers
5k views

IMG tag vulnerability

Is it safe to display images from arbitrary domains? I.e. let's say I have an image on my page: <img src="http://badguy.com/image.gif" /> What if image.gif will return some js attack vector, ...
22
votes
5answers
6k views

What are the security risks of letting the users upload content to my site?

As a web designer (not a security expert) I wonder: If I allow users to upload content to my website (videos, images and text files), what are the real risks involved?
21
votes
3answers
4k views

How can I be protected from pictures vulnerabilities?

I've just read this question What is the corrupted image vulnerability? How does it work? (GIFAR, EXIF data with javascript, etc..) I'm asking myself how can I protect myself and my website's users. ...
18
votes
3answers
3k views

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 ...
15
votes
4answers
3k views

What are the security threats of zip file uploads and what preventive actions should be taken?

We have a Drupal application developed for sharing files. We are allowing zip files to be uploaded by logged in departmental user. We are using Drupal private file system (outside webroot). We are ...
15
votes
3answers
14k views

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 ...
15
votes
4answers
1k views

Is it safe to store and replay user-provided mime types?

If a user uploads a file but modifies the request by setting the mime-type to something arbitrary, like "superdangerous/blackhatstuff", is it safe for me to send the same mime type back to a different ...
14
votes
5answers
6k views

Is there a way to check the filetype of a file uploaded using PHP?

I don't want it to just check the extension of the file as these can easily be forged even MIME types can be forged using tools like TamperData. So is there a better way to check file types in PHP ? ...
12
votes
3answers
3k views

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 ...
10
votes
4answers
3k views

Is it safe to serve any user uploaded file under only white-listed MIME content types?

Let's say I develop an application that, Allows any user to upload a file of only white listed mime content type and extensions (word and pdf). Serves those files with the allowed extension and ...
10
votes
2answers
6k views

Exploits or other security risks with SVG upload?

I have a site, where people can upload graphics, you might think of it like an image hoster or a forum for pictures. Now, I allow upload of raster graphics to a certain size, but no vector graphics ...
10
votes
3answers
3k views

What is the next step of this file upload attack?

Yesterday I discovered somebody had uploaded this PHP code to my server as a .jpg file via my asp.net MVC application's "Upload your profile picture" form. I believe the attack was unsuccessful for a ...
10
votes
1answer
5k views

.JPEG File upload shell via EXIF comments

I came across this advisory recently and I'm a bit confused by both exploits, but specifically the file upload vulnerability. I don't understand how to actually exploit this condition (or even why ...
9
votes
1answer
173 views

Security measures and anti-virus on server to mitigate acting as a propagation vector

We have a web application for which I've been asked to add the ability to let users upload documents that will then be visible and downloadable by other users. Those documents will typically be images ...
8
votes
4answers
1k views

Making a Blacklist of filetypes to protect PHP application

I'm working in a PHP system where the user can upload files. I'm trying to protect the system from malicious codes, so I'm thinking about some type of blacklist of files that I've to block from ...
8
votes
2answers
2k views

Why should I restrict the content type of files be uploaded to my site?

We are building an application where users can upload resumes in our system for our administrators to download. We are having a debate about restricting the content type of the files that can be ...
8
votes
2answers
3k views

Antivirus for scanning anonymous file uploads

Since I have no experience with AV solutions on Unix-like environments, I would need help with suggestions on something that can be suitable for scanning files that are uploaded by anonymous users ...
8
votes
3answers
9k views

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. ...
7
votes
1answer
2k views

How can I spoof the Mimetype of a file upload?

There are posts that says php mimetype isn't secure, or can be bypassed. How do people spoof the mimetype?
6
votes
4answers
370 views

Worst case scenario of having the ability to remotely write files to disk as admin

I'm working on creating a program ("My Program") that will communicate with another program ("Their Program") via XML commands over a raw TCP/IP connection. Their program allows files to be written to ...
6
votes
6answers
1k views

How to defend vs. Image Remote File Inclusion, e.g. RFI using a .gif file (Apache/PHP)?

To defend versus Remote File Inclusion where attackers try to abuse image files, I usually recommend to never use include to include image files into PHP code. Sometimes though, the avoidance of ...
6
votes
5answers
1k views

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 ...
6
votes
2answers
3k views

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 = ...
5
votes
3answers
13k views

How does SFTP function without a manually generated public/private key pair

I am learning about SSH and how to use it to secure file transfers and commands between a windows machine and a Linux server. Everything that I have read so far indicates that I need to use an SFTP ...
5
votes
3answers
862 views

is it safe to allow external images to be attached to Blog or any Web content?

I am filtering all images that attached to any content of my blog: Check for file extension. Check content type using $finfo = finfo_open(FILEINFO_MIME_TYPE); I also save the image temporary on my ...
5
votes
2answers
162 views

Exploiting a PHP server with a .jpg file upload

I would like to ask a question regarding the classic uploading an image and executing php code exploit on a website. So I have been trying out this exploit a website I'm supposed to hack (It's set up ...
5
votes
3answers
470 views

PHP | Security for allowing user uploads

My Sittuation: I am creating a web application with PHP which allows users to scan their files for viruses. It allows the user to upload their files via the html "file" input type or via a URL. I ...
4
votes
3answers
667 views

Is changing image's extension prone to error for browsers?

In my uploading user's avatar scenario, I change users picture extension to jpg. Is this making the browsers to act differently? Is it prone to error for browsers when they read users avatar? ...
4
votes
5answers
1k views

Clicked on fake “Download Now!” ad on file transfer site (legal file for legit purposes) by accident; does anyone know what measures I should take?

I was sent a file by a coworker via "sendshare" - my first time using the service. The page loaded a bit slowly and the ads came in before the actual download link. I was in a hurry to get the file - ...
4
votes
4answers
5k views

Is it necessary to scan users' file uploads by antivirus?

Web application allows users to upload files. Is it necessary to scan those files by antivirus? I'd want to hear answer in two scenarios: Type of file isn't checked when uploading. They are stored ...
4
votes
5answers
250 views

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 ...
4
votes
5answers
480 views

Is it dangerous to serve user-uploaded Flash (SWF) files?

I'm working on a site that has CMS functionality. I'm considering allowing users to upload Flash (.swf) files and then displaying them on my site. Is this a bad idea? Is there a way to do this ...
4
votes
1answer
1k views

One-Way Data Transfer Cable

Is there a cable that physically only supports data flow in one direction (out)? The idea here is to put this on a system that can only export data so that there is very minimal risk of the ...
4
votes
3answers
5k views

Is it possible for a hacker to bypass upload php file?

I wanna give a filtering system in my script. here it is : <?php $allowedExts = array("gif", "jpeg", "jpg", "png","bmp"); $temp = explode(".", $_FILES["file"]["name"]); $extension = end($temp); ...
4
votes
1answer
240 views

Is there a tree hash form of MAC that can be used when encrypting data for storage on S3 using multipart upload?

I am storing files on S3, some of which are very large, and need to be stored encrypted. I had planned on using Galois Counter Mode since it includes the MAC, however this won't work with multipart ...
3
votes
2answers
4k views

What does it mean to have a “file name with NULL bytes in serialized instances”?

I was browsing this page, which redirected me to this vulnerability because I'm a Java developer and I'm aware of the affected library. Basically the vulnerability says: It was discovered that ...
3
votes
2answers
736 views

Risks of serving untrusted content under HTTP Content-Type: text/plain?

Am I gonna run into XSS attacks by doing this, or will a file download be prompted? Are there security problems that would rise in a modern browser?
3
votes
2answers
51 views

After I've plugged my phone into a computer to upload photos, can people see the photos I did not upload even after I unplugged my phone?

I plugged my phone into a computer at work to upload photos using a USB, then unplugged it. I only uploaded the photos I needed, however, could they somehow see the photos I didn't upload on the ...
3
votes
1answer
34 views

“Public facing” dropbox folder uploads to admins machine. Potential security issues?

We've got a client who uses Wufoo for their website's forms. One of their forms contains a file upload feature, this is set in Wufoo to place the uploaded file into a Dropbox folder. This Dropbox ...
3
votes
1answer
525 views

What are security risks of serving user uploaded files without Content-Disposition?

Imagine a server that serves untrusted user-provided files and allows other users to download them. Under some circumstances server can be tricked to return responses to download file requests without ...
3
votes
2answers
36 views

Standard (or solution) for securing files in a point-to-point integration

I'm looking for a relatively light weight way to secure both integrity and confidentiality for files being uploaded in a point-to-point integration. The use case is uploading batch files for ...
3
votes
0answers
130 views

Is there a way my organization can collect clients' sensitive documents without being liable for them? [closed]

I am the head of IT for a microlending organization. We make small loans to new businesses, and as such we have to collect these clients' tax returns and other financial data as part of the ...
2
votes
3answers
212 views

How to test for presense of antivirus?

I want to test that when user uploads file, then it goes through up-to-date and properly configured antivirus. I think that to test for it I need some malware that is likely to be detected (it doesn't ...
2
votes
4answers
167 views

Secure File Sharing with China

I am looking for a convenient, and particularly a secure way to share files with business contacts in China. My priorities, in this order, are Secure, non-hackable. Accessible. I know many sites ...
2
votes
1answer
180 views

Bypass Text Plain Rule

I want to know if I can allow uploading all types of scripts and add these rules to a virtual host configuration; so please advise and tell me if there will be some exploits that can be used to ...
2
votes
2answers
172 views

Enforce a time limit on the number of uploads per user

I've done a lot of searching on SE and particularly here in regards to preventing issues or attacks for an image based website to accept image uploads, but I haven't seen anyone mention the idea of ...
2
votes
1answer
229 views

Prevent shell script inside image file

Recently, one of my website was hacked by someone who uploaded an image (shell.gif) to my server. I have put server side validation to check file extension + mime type of the image. However, they are ...
2
votes
3answers
683 views

Pentesting file Upload feature

The file(resume) upload feature is accepting any sort of files. I have uploaded the PHP shell into it. How do I again access to that uploaded file? I'm bruteforcing the web directory to check for ...
2
votes
1answer
236 views

Where to store uploaded images from perspective of security

It is quite common that uploaded files (images, videos, etc.) are stored on a file server because of performance and database-recovery-time reasons. But is there a benefit of storing such files in ...
2
votes
1answer
361 views

Uploading Executable Files

Using proxy software, I was able to bypass a file upload control file-checking for an asp.net system I am pen testing. I noticed they are saving the file into the database as bytes, and it is ...