Directory traversal vulnerability in cgi-bin/koha/mainpage.pl in Koha 3.4 before 3.4.7 and 3.6 before 3.6.1, and LibLime Koha 4.2 and earlier allows remote attackers to read arbitrary files via a .. (dot dot) in the KohaOpacLanguage cookie to cgi-bin/opac/opac-main.pl, related to Output.pm.
https://github.com/liblime/LibLime-Koha/commit/8ea6f7bc37d05a9ec25b5afbea011cf9de5f1e49#C4/Output.pm
https://exchange.xforce.ibmcloud.com/vulnerabilities/71478
http://secunia.com/advisories/46980