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.
