How to prevent html injection in fastapi?

@brandy 

To prevent HTML injection in FastAPI, you can use the built-in escaping capabilities of Jinja2 templates or the built-in HTML escaping functions provided by the FastAPI framework itself. Here are some steps you can take to prevent HTML injection in your FastAPI application:

1. Use the autoescape functionality of Jinja2 templates: Make sure to enable autoescaping in your Jinja2 templates by using the autoescape=True option when configuring the template environment. This will automatically escape all HTML characters in any variables that are rendered in the templates.
2. Use FastAPI's HTML escaping functions: FastAPI provides functions such as html.escape() and html.unescape() to escape and unescape HTML characters in input data. Make sure to use these functions to sanitize any user input that may contain HTML content before displaying it in your application.
3. Validate and sanitize user input: Implement validation checks on user input fields to ensure that they do not contain any malicious HTML content. You can use tools like the Bleach library to sanitize user input by stripping out any HTML tags or attributes that may pose a security risk.
4. Use secure form handling practices: Ensure that your forms use the POST method and employ CSRF protection to prevent malicious HTML injections through form submissions. FastAPI provides CSRF protection out of the box, so make sure to enable it in your application.

By following these best practices and implementing proper input validation and sanitization techniques, you can effectively prevent HTML injection attacks in your FastAPI application.