30 September
What happened on this date in privacy, anonymity networks and censorship. Every year on the same date we add a new look back and keep the earlier ones as they were.
2026
Certificate warnings on old phones
If your phone, or a family member's, is stuck on Android 7 or earlier, websites that use Let's Encrypt certificates show certificate warnings. Let's Encrypt is a free service that issues HTTPS certificates, and a phone trusts those sites only if it recognises the Let's Encrypt root certificate. The trust Let's Encrypt had borrowed from another certificate authority expired on 30 September 2021, and older Android versions held on for three more years through a specially issued certificate valid until 30 September 2024. In 2023 Let's Encrypt advised those phones to switch to Firefox, but in September 2025 Mozilla announced that Firefox 144 would support only Android 8.0 and later, leaving older phones on a version that no longer receives updates. To check, look up the Android version in your phone's settings.
Sources
DST Root CA X3 Expiration (September 2021)Let's Encrypt- Shortening the Let's Encrypt Chain of TrustLet's Encrypt,
Raising the Minimum Android Version for FirefoxMozilla,