Mozilla has released updates to address vulnerabilities in Firefox, Firefox ESR, and Thunderbird. It is recommended that you take the necessary precautions by ensuring your products are always updated.
Security vulnerabilities fixed in Firefox 67.0.4 and Firefox ESR 60.7.2
Security vulnerabilities fixed in Thunderbird 60.7.2
For more information on Microsoft May 2019 security updates you can follow this url:
Microsoft Releases Security Updates for Thunderbird: https://www.mozilla.org/en-US/security/advisories/mfsa2019-19/
The Guyana National CIRT recommends users and administration to review these updates and to apply them where necessary.
Microsoft release Security updates for Firefox, Thunderbird (US-Cert)