The CMS installer in Joomla! before 3.7.4 does not verify a user’s ownership of a webspace, which allows remote authenticated users to gain control of the target application by leveraging Certificate Transparency logs.
www.securitytracker.com/id/1039015
developer.joomla.org/security-centre/700-20170704-core-installer-lack-of-ownership-verification.html
media.defcon.org/DEF%20CON%2025/DEF%20CON%2025%20presentations/DEFCON-25-Hanno-Boeck-Abusing-Certificate-Transparency-Logs.pdf
twitter.com/hanno/status/890281330906247168