https://www.debian.org/security/2016/dsa-3628

The part that effects Koha is the @INC bit

The problem relates to Perl 5 ("perl") loading modules from the includes
directory array ("@INC") in which the last element is the current
directory ("."). For more information, see the RT ticket linked above.

While the Perl Security group has attempted to mitigate some of these
problems by modifying Perl Modules, it is ultimately the responsibility
of the application writer to remove relative paths from @INC to assure
the security / consistent behavior of their code regardless of what
directory it executes from.

The fix is to check if the last entry of @INC is "." and if so, to
remove it as an included path.

The following line, when added to the top of Perl applications, should
mitigate this problem. This assumes your code is not intentionally
depending on paths relative to your current working directory:

    BEGIN { pop @INC if $INC[-1] eq '.' }

We would also like to discourage using relative paths in @INC.

I only found 2 places where we set the @INC specifically inside Koha 
Specifically

Koha/Plugins.pm:    push @INC, C4::Context->config("pluginsdir");
Koha/Plugins/Handler.pm:    push @INC, C4::Context->config("pluginsdir");

Potentially if someone put . as the plugins dir in the config they would leave themselves open to this. While it is unlikely anyone would do this, we may as well add a fix to protect if they did.