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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394 views

File shares from a DMZ into an internal network

We have a firewall policy that prohibits MS RPC through firewall, particularly from internet facing DMZ's back to the internal network. There is a business unit requesting an alternative method to ...
32
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5answers
3k 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, ...
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1answer
1k 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?
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2answers
61 views

Per-transfer authorization of file transfers on a per transaction basis

In my organization, users have the rights to transfer files to and from servers using SSH File Transfer protocol for a variety of reasons; e.g. application troubleshooting, BAU, etc. Although our ...
5
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1answer
3k 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 ...
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4answers
2k 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 ...
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3answers
2k 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 ...
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2answers
229 views

Is there any risk in posting “local info” to the Internet?

Previously when I posted a screenshot online, someone told me to erase out my usernames, computer names, domain names, etc: Is there actually a need to do so? A quick Google search shows that many ...
5
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3answers
633 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 ...
2
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1answer
710 views

Methods for uploading shell to a website

I know shells can be uploaded via sql injection, remote file inclusion and exploiting the web app's own upload mechanism. Are there any other ways to upload a shell to a website and be able to execute ...
1
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6answers
8k views

Use PHP to check uploaded image file for malware?

I want my users to be able to upload a photo. Currently I am not checking the uploaded photo for problems of any kind, although I do limit the size to 32k. Is there any way for me to check uploaded ...
4
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1answer
201 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 ...
2
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1answer
1k views

File upload vulnerability: rename solution?

I have a module in which the user can upload images. I searched Google for different kinds of upload attacks checking dimension of the image (still vulnerable) checking of file extension ...
2
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4answers
3k 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 ...
2
votes
3answers
562 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
346 views

Is it safe to invoke PHP GD functions if you don't know whether file is a valid image?

There is image upload function in web application. After image is uploaded, it's resized using functions from PHP GD like imagecopyresampled and others. Before invocation of PHP GD's functions there ...
6
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4answers
363 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 ...
2
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1answer
402 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 ...
1
vote
4answers
676 views

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 ...
3
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2answers
637 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?
2
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3answers
207 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 ...
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 - ...
7
votes
3answers
6k 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. ...
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1answer
183 views

How to secure upload from desktop client to web application?

Let's say we have a desktop application and a web application. The desktop application uploads files to the server using POST requests to the web application. What are the possibilities (except using ...
9
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3answers
11k 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 ...
2
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2answers
998 views

Why should crossdomain.xml be present if user-uploaded files exist?

In his book Michal Zalewski says: To protect your users, include a top-level crossdomain.xml file with the permitted-cross-domain-policies parameter set to master-only or by-content-type, even if ...
7
votes
5answers
837 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
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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 = ...
9
votes
4answers
2k 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 ...
7
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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 ...
7
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2answers
4k 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 ...
1
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1answer
196 views

users avatar names based on Primary Key, is it safe?

We upload users avatar with their primary key name. avatars name are 1.jpg,2.jpg,3.jpg,... according to their primary key. We implemented this to omit avatar field from database, instead with use ...
4
votes
3answers
529 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? ...
6
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2answers
2k 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 ...
15
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4answers
918 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 ...
4
votes
5answers
193 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 ...
19
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3answers
3k 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. ...
10
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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 ...
5
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 ...
20
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5answers
5k 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?
18
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3answers
2k 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 ...