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How to prevent Cross-Site Scripting (XSS) in ASP.NET Core?

How to prevent cross-ste scripting(XSS) in Asp.Net Core

Preventing Cross-Site Scripting (XSS) attacks is crucial to the security of your ASP.NET Core applications. XSS attacks occur when an attacker injects malicious scripts into a web application, which are then executed by the victim's browser. Here are some measures you can take to prevent XSS attacks in ASP.NET Core:

1-Input Validation:
Ensure that all user inputs are validated on both the client and server sides. Use validation techniques such as regular expressions, white-listing, and proper data type validation to ensure that only expected input is accepted.
2-Output Encoding:
Always encode user input before rendering it in the HTML. This prevents the browser from interpreting the input as executable script code. In ASP.NET Core, you can use the HtmlEncoder class for output encoding.
3-Content Security Policy (CSP):
Implement Content Security Policy headers to control which resources are allowed to be loaded on your page. This helps to prevent the execution of malicious scripts by restricting the domains from which content can be loaded.
In your application's Startup.cs:
4-AntiXSS Library:
Consider using the AntiXSS library, which provides additional encoding functions specifically designed to prevent XSS attacks.
Install the AntiXSS library using NuGet:
In your code, use the HtmlEncoder.Default.Sanitize method:
5-Use Razor Pages and Tag Helpers:
When using Razor Pages and Tag Helpers in ASP.NET Core, they automatically handle HTML encoding for you. Always prefer using these features over manually rendering HTML.
6-Avoid using innerHTML:
If possible, avoid using innerHTML in JavaScript to dynamically inject content into your page, as it can expose your application to XSS vulnerabilities. Instead, use the DOM manipulation methods provided by the browser.
7-Regularly Update Dependencies:
Keep your ASP.NET Core framework and third-party libraries up to date to benefit from the latest security patches and improvements.
By implementing these best practices, you can significantly reduce the risk of XSS attacks in your ASP.NET Core application. Always remember that security is an ongoing process, and staying informed about the latest security trends and vulnerabilities is essential.




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About Author

Brijesh Kumar

Database Developer

I have more then 6 years Experience in Microsoft Technologies - SQL Server Database, ETL Azure Cloud - Azure SQL Database, CosmosDB, Azure Data Factory, PowerBI, Web Job, Azure Function, Azure Storage, Web Apps, Powershall and Database Migration On-Premise to Azure Cloud.
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