An application that is accessed over a network such as the Internet or an intranet using a browser.

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10
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8answers
2k views

What chars should I not allow in passwords?

I am planning to develop a website that require that the users register a username and a password. When I let the user choose a password, what chars should I allow the users to have in the password? ...
10
votes
6answers
3k views

Security review: “HTTP header user-agent has been set to (something)”

We got a security review done of our PHP code and they team advised this in their report (amongst other things): /appdir/ Details The HTTP header user-agent has been set to \" . Request GET ...
10
votes
4answers
368 views

Should a web application return true http errors?

Exception and error information can be used by a malicious user to map out the API of an web application, so it is routine to see security checklists to advise returning only a "Please contact your ...
10
votes
7answers
732 views

IP address black list

My website has a black list of IP addresses. The web application, in some way, detects all invalid, suspicious influences to it and remembers IP address and denies any requests from that IP address. ...
10
votes
5answers
10k views

Benefits of identifying clients based upon the “X-Forwarded-For” or similar HTTP header in addition to Client IP

The X-Forwarded-For header is used by some HTTP proxies to identify the IP address of the client. The wiki page (linked above) mentions that ISPs may use this header as well. In addition there are a ...
10
votes
3answers
260 views

What simple security considerations can I / should I make for a read-only API?

Right now I'm setting up an API, to be consumed on the client-side to set up a directory site. I'm wondering what extra steps I need to take just to prevent people from gaining write access to the ...
10
votes
2answers
7k views

Implications of Trace/Track Methods on Apache

When performing vulnerability scans using Nessus, against a host running Apache, one expected result is always "HTTP TRACE / TRACK Methods Allowed". While this result only has a base CVSS of 4.3, I ...
10
votes
3answers
2k 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
2answers
1k views

What are the SQL-injections issues of parameterized queries?

I've written some code to generate an SQL query in ASP classic. I'm not sure if it's secure or not: Set adoCon = Server.CreateObject("ADODB.Connection") adoCon.Open "Provider=Microsoft.Jet.OLEDB.4.0; ...
10
votes
2answers
4k views

What can an attacker do with a stolen SSL private key? What should the web admin do?

What can an attacker do with a stolen website certificate and key? What should the website admin do upon learning this?
10
votes
3answers
405 views

Should I ask a user to re-authenticate if the browser thumbprint changes? Is a server side library available?

Is there a security benefit to using the browser's thumbprint in addition to a session identifier to identify a unique session? Would it then be advisable to ask the user to reauthenticate (or simply ...
10
votes
2answers
270 views

Preventing Voter Fraud on a Social Media Contest

I'm creating a contest that will allow users to login using their Facebook & Twitter accounts and submit votes on videos. My clients concern is that users will game the system by logging into ...
10
votes
3answers
712 views

Is Gmail showing images by default a good idea for privacy?

Google have decided to show images in Gmail messages accessed via the web, iOS and Android by default: Instead of serving images directly from their original external host servers, Gmail will now ...
10
votes
1answer
448 views

Public XSLT & XML playground (with PHP DOMDocument, etc.) Security Risks?

Let's say I want to set up a sandbox or playground in PHP that users can use to create (or paste in) XML and XSLT, then transform the XML via the XSLT (by means of PHP 5's DOMDocument and related ...
10
votes
4answers
757 views

Sending HTTP 403 as. 200 - “Silent Identification of Admin”

A researcher recently reported an issue in a site about using script on a 3rd party site to discover if a user is an admin. Here's the scenario: Main site is target.example Attacker site is ...
10
votes
2answers
827 views

Security quiz for developers

Does anyone know of a short security quiz that could be administered online, to test the security knowledge of a developer? I'm looking for something simple to administer and simple to grade, ideally ...
10
votes
4answers
6k views

What are the disadvantages of single sign-on authentication?

We were discussing to implement single on in our web application,right now after analyzing we came to know that the following were the advantages of single sign on authentication. Advantages Users ...
10
votes
4answers
2k views

What is the right way of storing database connection strings from the security point of view?

What are recommendations, best practices and have-to-dos regarding handling connection strings in web applications? What things one should never, ever do?
10
votes
3answers
772 views

If I am obliged to store a password/certificate on a client side, how can i make sure that it is protected?

In certain cases we need to establish a key/password/certificate as a first timer and then as a client we need to use this key/password/certificate to get authenticated. Therefore the ...
10
votes
1answer
331 views

Is there a web application firewall equivalent of virustotal?

I'm wondering if there is a web application firewall (WAF) equivalent of VirusTotal? A site where I can throw for example injection strings, exploits or xss, and it will tell me what the default ...
10
votes
2answers
2k views

How to protect against clickjacking attack but allow legit iframes?

I'm aware of modern anti-clickjacking approaches, such as X-Frame-Options header or framekiller scripts. But all these tactics prevent content to be inside iframe. But what if there is a requirement ...
10
votes
3answers
1k views

How to perform penetration testing on a Flex application?

Possible Duplicate: What tools are there to inspect Flash SWF files? I have decompiled it, verified the source. All seems fine. Appscan also is not able to find anything in this case. But I ...
10
votes
1answer
748 views

How can I embed iframe securely without restricting its functionality?

I'd want to embed an iframe from untrusted site into web application. Iframe: should be able to run Javascript and browser plugins (Flash, etc.) should not be able to access my web application ...
9
votes
6answers
537 views

What are web attacks which users can run code on your servers?

I hear stories about insecure web servers and sites which people (or bots) break into and execute their own code on the server. My question is how is that possible? I heard of people putting their ...
9
votes
3answers
808 views

Why should I use whitelist on a WAF?

I was studying different WAFs, from open-source (such as ModSecurity and NAXSI) to commercial solutions (Imperva, Citrix, Fortinet, etc.). Many people state that having a whitelist-based WAF is far ...
9
votes
5answers
1k views

Ads appearing in our application when they should not be

I received a strange issue reported by one of my web application users. Apparently they are getting "ads" within the browser window when using my application. I didn't add advertisements at all. It's ...
9
votes
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 ...
9
votes
4answers
4k views

avoid hitting DB to authenticate a user on EVERY request in stateless web app architecture?

Summary Once a user logs into a web site and his username/password credentials are verified and an active session is established, is it possible to avoid hitting the DB for each and every request ...
9
votes
3answers
2k views

Is it possible to forge a post request?

Consider the following URL http://mysite.com/form?date=x. Suppose that if x is in an incorrect format, that a page is returned with <p>x is not a valid date</p>, where the page author has ...
9
votes
3answers
10k views

Is it possible to execute a php script in an image file? [duplicate]

I have an image upload php website. Users can upload images to my website. A user claims he can hack my website using an uploaded image. I opened all the images that he uploaded to my server with ...
9
votes
3answers
975 views

How do I secure my SaaS startup?

I came across this question I like to offer my startup also for security advice. Objective: building a SaaS web application that allows businesses to quickly open up online stores akin to Yahoo! ...
9
votes
4answers
292 views

What are the main security considerations that must be taken into account if you intend on creating a (localised) whistleblower website?

Also: Is it something that can be achieved with limited funds? I ask because I am intrigued by the obstacles that are in place.
9
votes
3answers
427 views

How could the string \";alert('XSS');// be used for XSS?

I was using Burp Suite for some testing and I noticed that they included the following string: \";alert('XSS');// as an attack string for an XSS payload. How could this string be used to execute ...
9
votes
4answers
4k views

How effective are reverse proxies as a web application security measure?

How effective are reverse proxies as a web application security device? Which types of threats do they mitigate against and which don't they? For example are they more effective in preventing ...
9
votes
4answers
506 views

Does my UI need to be secure if my API is?

I'm working on a project that is creating two new, separate web modules (possibly even on different servers) to support a new web application, with one serving up a static JS-based UI and the other ...
9
votes
3answers
3k views

Is there a way to bypass Django's XSS escaping with “unicode”?

Django (the Python web framework) escapes output to prevent XSS (Cross Site Scripting) attacks. It replaces ', ", <, >, & with their HTML safe versions. However this presentation on slide ...
9
votes
4answers
377 views

When changing a password using a WebPage, must the old password be entered on the same screen?

There is a convention to always prompt for the old password on the same page as the one where the old password is being changed as shown below. Is it acceptable from a security perspective to allow a ...
9
votes
4answers
993 views

How dangerous is it to store password in plain text on sites like GitHub?

I have a few private repositories set up on GitHub for some of the projects I am working on for my company. These applications connect to databases and I have database authentication credentials ...
9
votes
6answers
6k views

Why is php not used for banking sites or for a banking transaction?

Other programming languages popular on the web, such as Java and .NET, are used for banking sites. However, I've rarely (if ever) seen a PHP application designed to be deployed for a banking site. ...
9
votes
2answers
1k views

Security Concerns on clientside(Javascript)

We are going to design and implement a UI for a big website. Owner of the site is really cautious about security issues. I wonder if there is a check list for security issues at the client-side ,while ...
9
votes
1answer
538 views

XSS Technique - & JavaScript Include

I was looking through the OWASP XSS Filter Evasion Cheat Sheet, and there was one technique that was completely new to me: & JavaScript includes <BR SIZE="&{alert('XSS')}"> I ...
9
votes
4answers
605 views

Worthwhile from security standpoint to limit database server user for ASP.NET website to only EXECUTE on stored procedures?

I know that obviously we must avoid sql injection attacks through user input validation and parametrized queries. There's already a firewall in place on the database server to limit remote ...
9
votes
4answers
310 views

Defending site against being abused by phishing

Say you have a web site and you are using some returnUrl URL parameter to redirect user back to page where he was after login or editing some records in user area. Is there some standard way how to ...
9
votes
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 ...
9
votes
3answers
967 views

AES using derived keys / IVs. Does it introduce a weakness?

I'm looking for an efficient way to encrypt multiple fields in a database with AES using a single global key, used throughout a large web application. Obviously in order to re-use this key, a unique ...
9
votes
3answers
1k views

localStorage for apps over https. What expectations are there?

I run an online gradebook. To keep student data private, I transfer all data over https. Now, I'd like to use localStorage to avoid redundant calculations and server requests. However, according to ...
9
votes
4answers
1k views

Is there a typical step-by-step A-Z process for testing a Web site for possible exploits?

I'm interested less in the tools of the trade (there are many questions here already about that), and I am interested more in the process by which you would go about using those tools. So for ...
9
votes
2answers
611 views

User-specific Subdomains : JavaScript security

If I provide a public-facing website for users on my website at their own subdomain (e.g. bob.myapp.com) under their own control, can I allow them to execute arbitrary JavaScript without putting my ...
9
votes
1answer
1k views

Strict Transport Security — max_age value

I've been wondering what max-age should the HTTP Strict Transport Security header have. Both paypal and lastpass sites leave it very low: 500 (seconds = bit over 8 minutes) market.android.com has it ...
9
votes
1answer
1k views

How to make SQL injection in PostgreSQL's tsquery?

I think there is SQL injection vulnerability in an application I'm testing. This is seen when I enter malformed parameters into a search form. All exceptions are shown in format: PHP raised unknown ...