// :x: VULNERABLE - No authorization check
[HttpGet("{id}")]
public async Task<Employee> Get(string id)
    => await repo.GetByIdAsync(id);

// :white_check_mark: SECURE - Authorization enforced
[HttpGet("{id}")]
[PlatformAuthorize(Roles.Manager, Roles.Admin)]
public async Task<Employee> Get(string id)
{
    var employee = await repo.GetByIdAsync(id);

    // Verify access to this specific resource
    if (employee.CompanyId != RequestContext.CurrentCompanyId())
        throw new UnauthorizedAccessException();

    return employee;
}

// :x: VULNERABLE - Storing plain text secrets
var apiKey = config["ApiKey"];
await SaveToDatabase(apiKey);

// :white_check_mark: SECURE - Encrypt sensitive data
var encryptedKey = encryptionService.Encrypt(apiKey);
await SaveToDatabase(encryptedKey);

// Use secure configuration
var apiKey = config.GetValue<string>("ApiKey");  // From Azure Key Vault

// :x: VULNERABLE - SQL Injection
var sql = $"SELECT * FROM Users WHERE Name = '{name}'";
await context.Database.ExecuteSqlRawAsync(sql);

// :white_check_mark: SECURE - Parameterized query
await context.Users.Where(u => u.Name == name).ToListAsync();

// Or if raw SQL needed:
await context.Database.ExecuteSqlRawAsync(
    "SELECT * FROM Users WHERE Name = @p0", name);

// :x: VULNERABLE - No rate limiting
[HttpPost("login")]
public async Task<IActionResult> Login(LoginRequest request)
    => await authService.Login(request);

// :white_check_mark: SECURE - Rate limiting applied
[HttpPost("login")]
[RateLimit(MaxRequests = 5, WindowSeconds = 60)]
public async Task<IActionResult> Login(LoginRequest request)
    => await authService.Login(request);

// :x: VULNERABLE - Detailed errors in production
app.UseDeveloperExceptionPage();  // Exposes stack traces

// :white_check_mark: SECURE - Generic errors in production
if (env.IsDevelopment())
    app.UseDeveloperExceptionPage();
else
    app.UseExceptionHandler("/Error");

# Check for vulnerable packages
dotnet list package --vulnerable

# Update vulnerable packages
dotnet outdated

// :x: VULNERABLE - Weak password policy
if (password.Length >= 4) { }

// :white_check_mark: SECURE - Strong password policy
public class PasswordPolicy
{
    public bool Validate(string password)
    {
        return password.Length >= 12
            && password.Any(char.IsUpper)
            && password.Any(char.IsLower)
            && password.Any(char.IsDigit)
            && password.Any(c => !char.IsLetterOrDigit(c));
    }
}

// :x: VULNERABLE - No validation of external data
var userData = await externalApi.GetUserAsync(id);
await SaveToDatabase(userData);

// :white_check_mark: SECURE - Validate external data
var userData = await externalApi.GetUserAsync(id);
var validation = userData.Validate();
if (!validation.IsValid)
    throw new ValidationException(validation.Errors);
await SaveToDatabase(userData);

// :x: VULNERABLE - Logging sensitive data
Logger.LogInformation("User login: {Email} {Password}", email, password);

// :white_check_mark: SECURE - Redact sensitive data
Logger.LogInformation("User login: {Email}", email);
// Never log passwords, tokens, or PII

// :x: VULNERABLE - User-controlled URL
var url = request.WebhookUrl;
await httpClient.GetAsync(url);  // Could access internal services

// :white_check_mark: SECURE - Validate and restrict URLs
if (!IsAllowedUrl(request.WebhookUrl))
    throw new SecurityException("Invalid webhook URL");

private bool IsAllowedUrl(string url)
{
    var uri = new Uri(url);
    return AllowedDomains.Contains(uri.Host)
        && uri.Scheme == "https";
}

public class SensitiveDataHandler
{
    // Encrypt at rest
    public string EncryptForStorage(string plainText)
        => encryptionService.Encrypt(plainText);

    // Mask for display
    public string MaskEmail(string email)
    {
        var parts = email.Split('@');
        return $"{parts[0][0]}***@{parts[1]}";
    }

    // Never log sensitive data
    public void LogUserAction(User user)
    {
        Logger.LogInformation("User action: {UserId}", user.Id);
        // NOT: Logger.Log("User: {Email} {Phone}", user.Email, user.Phone);
    }
}

public async Task<IActionResult> Upload(IFormFile file)
{
    // Validate file type
    var allowedTypes = new[] { ".pdf", ".docx", ".xlsx" };
    var extension = Path.GetExtension(file.FileName).ToLowerInvariant();
    if (!allowedTypes.Contains(extension))
        return BadRequest("Invalid file type");

    // Validate file size
    if (file.Length > 10 * 1024 * 1024)  // 10MB
        return BadRequest("File too large");

    // Scan for malware (if available)
    if (!await antivirusService.ScanAsync(file))
        return BadRequest("File rejected by security scan");

    // Generate safe filename
    var safeFileName = $"{Guid.NewGuid()}{extension}";

    // Save to isolated storage
    await fileService.SaveAsync(file, safeFileName);

    return Ok();
}

# .NET vulnerability scan
dotnet list package --vulnerable

# Outdated packages
dotnet outdated

# Secret scanning
grep -r "password\|secret\|apikey" --include="*.cs" --include="*.json"

# Hardcoded credentials
grep -r "Password=\"" --include="*.cs"
grep -r "connectionString.*password" --include="*.json"

var isAdmin = request.IsAdmin;  // User-supplied!

catch (Exception ex) { return BadRequest(ex.ToString()); }

var apiKey = "sk_live_xxxxx";

// No audit trail for sensitive operations
await DeleteAllUsers();