PII is redacted or screened before AI API calls

GDPR Article 25 mandates data protection by design — minimizing the personal data transmitted to processors. OWASP A02 (Cryptographic Failures) and CWE-359 (Exposure of Private Information) both apply when PII travels unredacted to a third party. Users routinely paste email addresses, phone numbers, credit card numbers, and SSNs into chat interfaces without realizing the consequences. Without a server-side screening pass, every one of those values is sent verbatim to the AI provider, where it persists in their logs and training pipelines according to their retention policies — not yours. The 2023 Samsung incident, where employees pasted internal code into ChatGPT, is the canonical example of this failure mode.

Implement a server-side redaction pass in lib/ai/pii-guard.ts and apply it before every AI API call. Server-side is mandatory — client-side filtering is bypassable.

// lib/ai/pii-guard.ts
const EMAIL_RE = /\b[a-zA-Z0-9._%+\-]+@[a-zA-Z0-9.\-]+\.[a-zA-Z]{2,}\b/g
const PHONE_RE = /(\+?1[\s.-]?)?\(?\d{3}\)?[\s.-]?\d{3}[\s.-]?\d{4}/g
const CC_RE = /\b\d{4}[\s\-]?\d{4}[\s\-]?\d{4}[\s\-]?\d{4}\b/g

export function redactPii(input: string): string {
  return input
    .replace(EMAIL_RE, '[EMAIL]')
    .replace(PHONE_RE, '[PHONE]')
    .replace(CC_RE, '[CARD]')
}

Apply before every AI invocation:

const safePrompt = redactPii(userInput)
const response = await openai.chat.completions.create({
  messages: [{ role: 'user', content: safePrompt }]
})

For higher-assurance use cases, AWS Comprehend DetectPiiEntities covers 100+ PII types. Verify with a unit test: pass an email address string and assert the AI mock receives [EMAIL].