webhooks/base.py in Anymail (aka django-anymail) before 1.2.1 is prone to a timing attack vulnerability on the WEBHOOK_AUTHORIZATION secret, which allows remote attackers to post arbitrary e-mail tracking events.
https://www.debian.org/security/2018/dsa-4107
https://github.com/anymail/django-anymail/releases/tag/v1.3
https://github.com/anymail/django-anymail/releases/tag/v1.2.1
https://github.com/anymail/django-anymail/commit/db586ede1fbb41dce21310ea28ae15a1cf1286c5
https://github.com/anymail/django-anymail/commit/c07998304b4a31df4c61deddcb03d3607a04691b