A maliciously constructed svn+ssh:// URL would cause Subversion clients before 1.8.19, 1.9.x before 1.9.7, and 1.10.0.x through 1.10.0-alpha3 to run an arbitrary shell command. Such a URL could be generated by a malicious server, by a malicious user committing to a honest server (to attack another user of that server's repositories), or by a proxy server. The vulnerability affects all clients, including those that use file://, http://, and plain (untunneled) svn://.
https://www.oracle.com/security-alerts/cpuoct2020.html
https://support.apple.com/HT208103
https://subversion.apache.org/security/CVE-2017-9800-advisory.txt
https://security.gentoo.org/glsa/201709-09
https://confluence.atlassian.com/sourcetreekb/sourcetree-security-advisory-2017-08-11-933099891.html
https://access.redhat.com/errata/RHSA-2017:2480
http://www.securitytracker.com/id/1039127
http://www.securityfocus.com/bid/100259
http://www.securityfocus.com/archive/1/540999/100/0/threaded
http://www.debian.org/security/2017/dsa-3932
http://packetstormsecurity.com/files/143722/Apache-Subversion-Arbitrary-Code-Execution.html