# External source check (CAC-20260831)

Checked 2026-09-04 with `scripts/verify-external-sources.py` (GET, follow redirects, 25s timeout). None of these pages audited this fixture. Machine log: [`external-source-check-CAC-20260831.json`](./external-source-check-CAC-20260831.json).

| Source | Requested URL | Final URL | HTTP | Title SHA-256 | Note | Use |
|---|---|---|---|---|---|---|
| Klaviyo S-1 | https://www.sec.gov/Archives/edgar/data/1835830/000162828023031916/klaviyoincs-1a.htm | https://www.sec.gov/Archives/edgar/data/1835830/000162828023031916/klaviyoincs-1a.htm | 200 | d6bd8c0aeee80fed |  | One public-company example defines CAC payback against cumulative non-GAAP gross profit and adjusted selling/marketing expense. |
| Retail Media Measurement Guidelines | https://www.iab.com/wp-content/uploads/2024/01/IAB_Retail_Media_Measurement_Guidelines_January2024.pdf | https://www.iab.com/wp-content/uploads/2024/01/IAB_Retail_Media_Measurement_Guidelines_January2024.pdf | 200 | — |  | Attribution windows, methods, viewability, and bias controls should be disclosed consistently. |
| Data-driven attribution | https://support.google.com/google-ads/answer/6394265?hl=en | https://support.google.com/google-ads/answer/6394265?hl=en | 200 | 2a6f6c15e57cc615 |  | Google documents advertiser-specific path comparison and credit allocation. |
| Invoice object | https://docs.stripe.com/api/invoices/object?api-version=2026-01-28.clover | https://docs.stripe.com/api/invoices/object?api-version=2026-01-28.clover | 200 | ab275f1fac66f783 |  | Documents customer, billing reason, status, amount, currency, timestamps, and line-item periods. |
| PPI WPU366 API | https://api.bls.gov/publicAPI/v2/timeseries/data/WPU366?startyear=2025&endyear=2026 | https://api.bls.gov/publicAPI/v2/timeseries/data/WPU366?startyear=2025&endyear=2026 | 200 | — |  | Public producer-price observations for internet advertising sales. |

Keep original requested URLs. Re-check at decision time.