Bug 19100 - XSS Flaws in memberentry.pl

Bug 19100 - XSS Flaws in memberentry.pl

1. Hit /cgi-bin/koha/members/memberentry.pl?op=add&guarantorid=xx<script>alert('amit')</script>
   xx - is a guarantorid
2. Notice the java script is executed.
3. Apply patch.
4. Reload page, and hit the page again /cgi-bin/koha/members/memberentry.pl?op=add&guarantorid=xx<script>alert('amit')</script>
   xx - is a guarantorid.
5. Notice it is no longer executed.

NOTE: I had to test in Microsoft Edge, because Chrome was blocking XSS for me.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>