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Lack of data validation - Modify DOM Elements


Implementation of robust data validation and sanitization mechanisms


  • Requirement of Ruby 2.0 or higher for running the application
  • Usage of Rails framework for building web applications


Non compliant code

def create
@post =[:post])

In the code snippet above, the application is using Ruby on Rails to create new posts. The posts are created from parameters received from the user input (params[:post]). This represents a lack of data validation, as the application does not check the content of the user input before creating the new post.

The params[:post] can contain any data that the user decides to send, including potentially harmful data. This can lead to a number of vulnerabilities. For instance, if the user input is extremely large, it can cause a buffer overflow. Alternatively, if the user input is designed to manipulate the system, it can cause memory corruption.

Moreover, because the application is directly using the user input to create new DOM elements, this can also lead to the creation and exploitation of other vulnerabilities. For example, an attacker could inject malicious scripts into the user input, which would then be executed by the application. This is known as a Cross-Site Scripting (XSS) attack.

To mitigate this vulnerability, the application should implement proper data validation. It should check the user input for any potentially harmful data before using it to create new posts. This could be done using a variety of methods, such as input sanitization or input validation.


  • Implement server-side data validation to ensure that only valid and expected data is accepted.
  • Validate the user-controlled inputs before using them to create dynamic DOM elements.
  • Use strong parameterization or whitelist approach to only allow specific attributes to be assigned to the Post object.
  • Sanitize user inputs to prevent any potential injection attacks.
  • Implement input validation rules to check for the expected data types, length, and format.
  • Consider using a validation library or framework provided by Ruby on Rails to simplify the validation process.
  • Regularly update and patch the Ruby on Rails framework to benefit from the latest security fixes and improvements.
  • Perform regular security audits and penetration testing to identify and address any potential vulnerabilities in the application.
  • Educate developers about secure coding practices and the importance of input validation to prevent similar vulnerabilities in the future.

Compliant code

class PostsController < ApplicationController
before_action :set_post, only: [:show, :edit, :update, :destroy]

# ...

def create
@post =
redirect_to @post, notice: 'Post was successfully created.'
render :new

# ...


# Use strong parameters to prevent unwanted assignment of attributes
def post_params
params.require(:post).permit(:title, :content)

The updated code now uses the strong parameters feature provided by Ruby on Rails to prevent unwanted assignment of attributes. This is done by defining a private method post_params that specifies the permitted parameters for a post.

In the create method, instead of directly using params[:post] to create a new post, post_params is used. This ensures that only the :title and :content attributes can be assigned through the form.

If any other parameters are included in the request, they will be ignored, preventing potential manipulation of the DOM elements.

In addition, the save method is now wrapped in an if statement. If the post is successfully saved, the user is redirected to the new post with a success message. If the post is not saved (for example, if it fails validation), the new post form is rendered again, giving the user a chance to correct their input.

This approach not only fixes the vulnerability but also improves the user experience by providing feedback on the success or failure of their action.

Remember to always validate and sanitize user inputs, use strong parameters, and keep your Ruby on Rails framework updated to the latest version to benefit from the latest security fixes and improvements. Regular security audits and penetration testing can also help identify and address potential vulnerabilities.