Looks like Mozilla revoked and rotated their signing key: https://blog.mozilla.org/security/2026/08/10/updated-gpg-key-for-signing-firefox-and-thunderbird-releases/.
==> Verifying source file signatures with gpg...
20260816-214904-firefox-156.0a1.en-US.linux-x86_64.tar.xz ... FAILED (unknown public key 678E455D76767AA3)
Pinned Comments
Sving1024 commented on 2025-04-12 13:48 (UTC)
@NoSohoth the master key is not outdated at all. please manually update your key.
VitalyR commented on 2024-10-09 08:27 (UTC)
Please submit patches to the GitHub repository for this package at https://github.com/VitalyAnkh/firefox-nightly-bin. Thank you for your help!
VitalyR commented on 2023-06-13 16:19 (UTC) (edited on 2023-06-13 16:29 (UTC) by VitalyR)
@tjhexf The PGP key is not outdated. Maybe there is some problem within your key server so you could try importing the key manually:
as @aag said.