Mozilla Foundation Security Advisory 2018-13 that mentions the bug #1411592 related to EFAIL (which is still closed today [summer 2022]). According to Ptacek's timeline, it was sent on October 25, 2017.
https://www.mozilla.org/en-US/security/advisories/mfsa2018-13/
Critical Commentary
Mozilla Foundation Security Advisory 2018-13 that mentions the bug #1411592 related to EFAIL (which is still closed today [summer 2022]). According to Ptacek's timeline, it was sent on October 25, 2017.