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.
https://twitter.com/hanno/status/890281330906247168
https://media.defcon.org/DEF%20CON%2025/DEF%20CON%2025%20presentations/DEFCON-25-Hanno-Boeck-Abusing-Certificate-Transparency-Logs.pdf
https://developer.joomla.org/security-centre/700-20170704-core-installer-lack-of-ownership-verification.html
http://www.securitytracker.com/id/1039015
Source: Mitre, NVD
Published: 2017-08-02
Updated: 2017-08-04
Base Score: 6.5
Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:P
Severity: Medium
Base Score: 8.8
Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: High