Mozilla Revokes GPG Signing Key After Accidental Upload to Private GitHub Repository

Mozilla has replaced the GPG key used to sign certain Firefox and Thunderbird builds following an accidental exposure of the unencrypted secret key in a private GitHub repository. The key was intended for signing Linux archives, RPM packages, and checksum files, raising theoretical risks of supply-chain attacks through forged installers. Company audits found no evidence of external misuse, as repository access was limited to a small group of employees who already held legitimate access to the key. Most users require no action, though those manually verifying GPG signatures must import the new key along with revocation data for the old one. Linux administrators installing Firefox via RPM packages on distributions such as Fedora, RHEL, Rocky Linux, AlmaLinux, openSUSE, and SUSE may need to manually update the key to avoid installation failures. Thunderbird users are unaffected by the RPM issue since no official RPM packages are released for the email client. The new key remains valid until August 5, 2028, with public details available in updated KEY files and on keys.openpgp.org.

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Mozilla has revoked and replaced a GPG signing key after an unencrypted copy of the secret key was accidentally uploaded to a private GitHub repository. The key had been used to sign Linux archives, RPM packages, and associated checksum files for Firefox and Thunderbird.

The incident created a theoretical risk that an attacker could have used the key to sign malicious installers and present them as official releases. However, Mozilla assessed the supply-chain risk as low because the repository was accessible only to a limited group of internal employees who already possessed legitimate access to the key.

Audit log reviews showed no indications that the key had been accessed or misused by unauthorized parties. As a result, the company revoked the old key and issued a replacement that will remain valid until 5 August 2028.

Most end users do not need to take any action. Individuals who manually verify GPG signatures on downloaded files must import the new public key and the revocation certificate for the previous key.

Users installing Firefox from RPM packages on Linux distributions may face additional steps. Depending on the distribution, they will need to update the signing key manually; otherwise, newer browser versions may fail to install. Mozilla has published specific instructions for Fedora, RHEL, Rocky Linux, AlmaLinux, openSUSE, and SUSE.

Thunderbird users are not affected by the RPM-related instructions because the mail client does not provide official RPM packages. Updated public key material and revocation information are available in the current KEY files for Firefox Nightly and on the keys.openpgp.org server.

Mozilla stated it will implement additional safeguards to prevent secret keys from being committed to repositories in the future.

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