A successful cross site scripting attack can have devastating consequences for an online business’s reputation and its relationship with its clients.

Depending on the severity of the attack, user accounts may be compromised, Trojan horse programs activated and page content modified, misleading users into willingly surrendering their private data. Finally, session cookies could be revealed, enabling a perpetrator to impersonate valid users and abuse their private accounts.

Cross site scripting attacks can be broken down into two types: stored and reflected.

Stored XSS, also known as persistent XSS, is the more damaging of the two. It occurs when a malicious script is injected directly into a vulnerable web application.

Reflected XSS involves the reflecting of a malicious script off of a web application, onto a user’s browser. The script is embedded into a link, and is only activated once that link is clicked on.

The ALTER TABLE statement is used to add, delete, or modify columns in an existing table.

The ALTER TABLE statement is also used to add and drop various constraints on an existing table.

ALTER TABLE - ADD Column

To add a column in a table, use the following syntax:

The following code is vulnerable to SQL injection because the user input is concatenated directly into the query:

String query = "SELECT * FROM products WHERE category = '"+ input + "'";

Statement statement = connection.createStatement();

ResultSet resultSet = statement.executeQuery(query);

This code can be easily rewritten in a way that prevents the user input from interfering with the query structure:

PreparedStatement statement = connection.prepareStatement("SELECT * FROM products WHERE category = ?");

statement.setString(1, input);

ResultSet resultSet = statement.executeQuery();

Parameterized queries can be used for any situation where untrusted input appears as data within the query, including the WHERE clause and values in an INSERT or UPDATE statement. They can't be used to handle untrusted input in other parts of the query, such as table or column names, or the ORDER BY clause. Application functionality that places untrusted data into those parts of the query will need to take a different approach, such as white-listing permitted input values, or using different logic to deliver the required behavior.

For a parameterized query to be effective in preventing SQL injection, the string that is used in the query must always be a hard-coded constant, and must never contain any variable data from any origin. Do not be tempted to decide case-by-case whether an item of data is trusted, and continue using string concatenation within the query for cases that are considered safe. It is all too easy to make mistakes about the possible origin of data, or for changes in other code to violate assumptions about what data is tainted.

https://insecure-website.com/products?category=Gifts

This causes the application to make an SQL query to retrieve details of the relevant products from the database:

SELECT * FROM products WHERE category = 'Gifts' AND released = 1

This SQL query asks the database to return:

• all details (*)
• from the products table
• where the category is Gifts
• and released is 1.

The restriction released = 1 is being used to hide products that are not released. For unreleased products, presumably released = 0.

The application doesn't implement any defenses against SQL injection attacks, so an attacker can construct an attack like:

https://insecure-website.com/products?category=Gifts'--

This results in the SQL query:

SELECT * FROM products WHERE category = 'Gifts'--' AND released = 1

The key thing here is that the double-dash sequence -- is a comment indicator in SQL, and means that the rest of the query is interpreted as a comment. This effectively removes the remainder of the query, so it no longer includes AND released = 1. This means that all products are displayed, including unreleased products.

Going further, an attacker can cause the application to display all the products in any category, including categories that they don't know about:

https://insecure-website.com/products?category=Gifts'+OR+1=1--

This results in the SQL query:

SELECT * FROM products WHERE category = 'Gifts' OR 1=1--' AND released = 1

The modified query will return all items where either the category is Gifts, or 1 is equal to 1. Since 1=1 is always true, the query will return all items.

.NET Core is a general purpose development platform maintained by Microsoft and the .NET community on GitHub. It is cross-platform, supporting Windows, macOS and Linux, and can be used in device, cloud, and embedded/IoT scenarios.

The following characteristics best define .NET Core:

• Flexible deployment: Can be included in your app or installed side-by-side user- or machine-wide.

• Cross-platform: Runs on Windows, macOS and Linux; can be ported to other OSes. The supported Operating Systems (OS), CPUs and application scenarios will grow over time, provided by Microsoft, other companies, and individuals.

• Command-line tools: All product scenarios can be exercised at the command-line.

• Compatible: .NET Core is compatible with .NET Framework, Xamarin and Mono, via the .NET Standard Library.

• Open source: The .NET Core platform is open source, using MIT an Apache 2 licenses. Documentation is licensed under CC-BY. .NET Core is a .NET Foundation project.

• Supported by Microsoft: .NET Core is supported by Microsoft, per .NET Core Support

More on the Official .NET Core Documentation from Microsoft

Basically, Microsoft built a version of .NET to allow developers to write cross-platform and cloud-optimized applications.

First, .NET is cross-platform. It runs on Windows, macOS and Linux, which allows the developer to share and run the exact same code between machines running different operating systems, with no changes in code and minimum or no changes in the development process. (Watch out for OS specific APIs!)

But the true innovation in .NET came with the modularization in design and architecture. The compiler (Roslyn) and the runtime (CoreCLR) are separate components that allow you to use different implementations (or even write your own).

Every library comes as a NuGet package, so when you start a new project, you don’t have any libraries, but a project file (currently a .json, in the future a .csproj to maintain consistency with all .NET projects) and a Program.cs. As you develop your app, you add libraries as you need them, allowing you to minimize the size of your application.

.NET Core also allows you to have multiple versions installed at the same time without having apps / parts of the OS breaking when you update or install a newer version of the framework, and will even allow you to ship the framework / parts of the framework with the application (since the footprint of the framework si small enough).

Nell'accezione odierna, la tecnica ricomprende l'utilizzo di qualsiasi linguaggio di scripting lato client tra i quali JavaScript, VBScript, Flash. Il loro effetto può variare da un piccolo fastidio a un significativo rischio per la sicurezza, a seconda della sensibilità dei dati trattati nel sito vulnerabile e dalla natura delle strategie di sicurezza implementate dai proprietari del sito web.

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Se pensate che una cosa simile possa accadere solo al cinema, vi ricrederete: questa scena viene girata ogni giorno decine, se non centinaia di volte, a causa di una delle tecniche di hacking del web più diffuse: la SQL injection. L’introduzione romanzata non esagera riguardo alla semplicità con cui un aggressore può oltrepassare i login messi a protezione delle nostre applicazioni web: è davvero questione di secondi.