diff --git a/Changelog.md b/Changelog.md
index e94c99ae6..911c04b99 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -6,6 +6,12 @@
 
 ## Features
 
+# 0.5.9.1
+
+Update Nokogiri to 1.6.8, which in turn updates libxml2 to 2.9.4 and libxslt to 1.1.29,
+addressing a range of security issues. See https://groups.google.com/forum/#!topic/ruby-security-ann/RCHyF5K9Lbc
+for more details.
+
 # 0.5.9.0
 
 ## Refactor
diff --git a/Gemfile b/Gemfile
index faff0c8e7..36f0439f5 100644
--- a/Gemfile
+++ b/Gemfile
@@ -126,7 +126,7 @@ gem "messagebus_ruby_api", "1.0.3"
 
 # Parsing
 
-gem "nokogiri",          "1.6.7.2"
+gem "nokogiri",          "1.6.8"
 gem "redcarpet",         "3.3.4"
 gem "twitter-text",      "1.13.4"
 gem "roxml",             "3.1.6"
diff --git a/Gemfile.lock b/Gemfile.lock
index f022f0346..350574f88 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -468,7 +468,7 @@ GEM
     mime-types-data (3.2016.0221)
     mimemagic (0.3.1)
     mini_magick (4.5.1)
-    mini_portile2 (2.0.0)
+    mini_portile2 (2.1.0)
     minitest (5.8.4)
     mobile-fu (1.3.1)
       rack-mobile-detect
@@ -482,8 +482,9 @@ GEM
     nenv (0.3.0)
     nested_form (0.3.2)
     nio4r (1.2.0)
-    nokogiri (1.6.7.2)
-      mini_portile2 (~> 2.0.0.rc2)
+    nokogiri (1.6.8)
+      mini_portile2 (~> 2.1.0)
+      pkg-config (~> 1.1.7)
     notiffany (0.0.8)
       nenv (~> 0.1)
       shellany (~> 0.0)
@@ -520,6 +521,7 @@ GEM
     parser (2.3.1.0)
       ast (~> 2.2)
     phantomjs (2.1.1.0)
+    pkg-config (1.1.7)
     powerpack (0.1.1)
     pry (0.10.3)
       coderay (~> 1.1.0)
@@ -852,7 +854,7 @@ DEPENDENCIES
   minitest
   mobile-fu (= 1.3.1)
   mysql2 (= 0.4.4)
-  nokogiri (= 1.6.7.2)
+  nokogiri (= 1.6.8)
   omniauth (= 1.3.1)
   omniauth-facebook (= 3.0.0)
   omniauth-tumblr (= 1.2)
@@ -925,4 +927,4 @@ DEPENDENCIES
   will_paginate (= 3.1.0)
 
 BUNDLED WITH
-   1.12.1
+   1.12.5
diff --git a/config/defaults.yml b/config/defaults.yml
index d32ed1c3e..11a28906c 100644
--- a/config/defaults.yml
+++ b/config/defaults.yml
@@ -4,7 +4,7 @@
 
 defaults:
   version:
-    number: "0.5.9.0" # Do not touch unless doing a release, do not backport the version number that's in master
+    number: "0.5.9.99" # Do not touch unless doing a release, do not backport the version number that's in master
   heroku: false
   environment:
     url: "http://localhost:3000/"