A persistent XSS could be injected via a filename commited to a SVN repo.
Impact
An attacker could use this vulnerability to force a victim to execute uncontrolled code.
CVSS2 score: 3.5 (AV:N/AC:M/Au:S/C:N/I:P/A:N)
CVSS3 score: 5.0 (3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:L/A:N)
Exploitation
Add a file in a SVN repo with a name like <img src="#" onerror="alert(1)">, commit your file and go to the detailed view of the file in subversion browser. The XSS will be triggered.
References
https://cwe.mitre.org/data/definitions/79.html
https://www.owasp.org/index.php/Cross-site_Scripting_%28XSS%29