Always sanitize input data before using it in sensitive operations to prevent injection vulnerabilities. This applies to shell commands, file operations, and URL handling. For shell commands: ```ruby # VULNERABLE: Direct interpolation of variables into command full_command = `#{HOMEBREW_BREW_FILE} #{brew_command} #{argument}` # SECURE: Escape each argument properly require 'shellwords' full_command = [HOMEBREW_BREW_FILE, brew_command, argument].compact .map { |arg| Shellwords.escape(arg) } ``` For file operations: ```ruby # VULNERABLE: Using IO.read/Kernel.open with non-constant values content = IO.read(filepath) # SECURE: Use File.read instead content = File.read(filepath) ``` For URL operations: ```ruby # VULNERABLE: Using URI.open with non-constant values response = URI.open(generated_url).read # SECURE: Use URI().open instead response = URI(generated_url).open.read ``` These patterns help prevent several classes of security vulnerabilities, including command injection, arbitrary file access, and server-side request forgery. Always assume input data could be malicious and handle it accordingly.