The parameter filename of the page /file/confirm_download.php could be exploited to create a HTTP response splitting or to force an user to do an unwanted action.
Impact
An attacker could use this vulnerability to force a victim to execute uncontrolled code or to do unwanted action.
CVSS2 score: 3.5 (AV:N/AC:M/Au:S/C:N/I:P/A:N)
Exploitation
HTTP Response Splitting: <tuleap_url>/file/confirm_download.php?popup=1&group_id=XXX&file_id=X&filename=name<CRLF><Attacker HTTP Request>
Uncontroled redirection: <tuleap_url>/file/confirm_download.php?group_id=XXX&file_id=X&filename=../../../../../account/logout.php
References
https://cwe.mitre.org/data/definitions/113.html
https://www.owasp.org/index.php/HTTP_Response_Splitting