This is:
http://www.berklix.com/~jhs/src/bsd/fixes/FreeBSD/src/gen/usr.sbin/wpa/wpa_supplicant/wpa_supplicant.conf.5.REL=ALL.diff
It was filed as:
https://bz-attachments.freebsd.org/attachment.cgi?id=147946
From:
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=194122

4.11-RELEASE has no /usr/src/usr.sbin/wpa/wpa_supplicant/*
It fails to apply to 13.2-RELEASE

*** 11.0-CURRENT-2014-10-03/src/usr.sbin/wpa/wpa_supplicant/wpa_supplicant.conf.5	Fri Oct  3 13:46:03 2014
--- new/src/usr.sbin/wpa/wpa_supplicant/wpa_supplicant.conf.5	Fri Oct  3 22:51:07 2014
***************
*** 138,143 ****
--- 138,153 ----
  Access points that cloak themselves by not broadcasting their SSID
  require technique 1, but beware that this scheme can cause scanning
  to take longer to complete.
+ .br
+ Security Caution: If you assert scan_ssid=1 (Instead of default scan_ssid=0):
+ .in +2
+ Instead of just sending a broadcast Probe Request frame,
+ FreeBSD would also send directed Probe Request frames with specific names.
+ Those network names would be observable to hostile 3rd parties,
+ & could be abused as per
+ http://www.bbc.com/news/technology-28891937
+ http://lists.freebsd.org/pipermail/freebsd-wireless/2014-October/005097.html
+ .in -2
  .It Va bssid
  Network BSSID (typically the MAC address of the access point).
  .It Va priority