When processing markdown content, always verify what sanitization your chosen markdown library provides to prevent XSS vulnerabilities while avoiding redundant security measures. Some libraries like `github_flavored_markdown` include built-in sanitization, while others like `blackfriday` require explicit sanitization of their output. Before adding sanitization calls, check the library documentation to understand its security features. For libraries without built-in sanitization: ```go // blackfriday requires explicit sanitization body := string(blackfriday.MarkdownCommon(input)) sanitized := bluemonday.UGCPolicy().SanitizeBytes([]byte(body)) ``` For libraries with built-in sanitization, avoid double-sanitization: ```go // github_flavored_markdown already sanitizes - no additional sanitization needed body := string(gfm.Markdown(input)) ``` This prevents both security gaps from missing sanitization and performance issues from redundant sanitization calls.