diff --git a/src/General/Settings.coffee b/src/General/Settings.coffee
index 0b17bfb14..5fe09c685 100644
--- a/src/General/Settings.coffee
+++ b/src/General/Settings.coffee
@@ -436,7 +436,7 @@ Settings =
       $.id('lastarchivecheck').textContent = 'never'
 
     items = {}
-    for name in ['archiveLists', 'archiveAutoUpdate', 'captchaLanguage', 'boardnav', 'time', 'backlink', 'fileInfo', 'QR.personas', 'favicon', 'usercss', 'customCooldown']
+    for name in ['archiveLists', 'archiveAutoUpdate', 'captchaLanguage', 'boardnav', 'time', 'backlink', 'fileInfo', 'QR.personas', 'favicon', 'usercss', 'customCooldown', 'jsWhitelist']
       items[name] = Conf[name]
       input = inputs[name]
       event = if name in ['archiveLists', 'archiveAutoUpdate', 'QR.personas', 'favicon', 'usercss'] then 'change' else 'input'
diff --git a/src/General/Settings/Advanced.html b/src/General/Settings/Advanced.html
index 211f0294d..cc246798d 100644
--- a/src/General/Settings/Advanced.html
+++ b/src/General/Settings/Advanced.html
@@ -140,3 +140,9 @@
   <button id="apply-css">Apply CSS</button>
   <textarea name="usercss" class="field" spellcheck="false"></textarea>
 </fieldset>
+
+<fieldset>
+  <legend>Javascript Whitelist</legend>
+  <div>Sources from which Javascript is allowed to be loaded by <a href="http://content-security-policy.com/#source_list" target="_blank">Content Security Policy</a>.</div>
+  <textarea name="jsWhitelist" class="field" spellcheck="false"></textarea>
+</fieldset>
diff --git a/src/config/Config.coffee b/src/config/Config.coffee
index d89e6c438..15071db74 100644
--- a/src/config/Config.coffee
+++ b/src/config/Config.coffee
@@ -792,6 +792,16 @@ Config =
     """
     sjisPreview: false
 
+  jsWhitelist: '''
+    http://s.4cdn.org
+    https://s.4cdn.org
+    http://www.google.com
+    https://www.google.com
+    https://www.gstatic.com
+    'unsafe-inline'
+    'unsafe-eval'
+  '''
+
   captchaLanguage: ''
 
   time: '%m/%d/%y(%a)%H:%M:%S'
diff --git a/src/main/Main.coffee b/src/main/Main.coffee
index 2975579a6..06e70ee48 100644
--- a/src/main/Main.coffee
+++ b/src/main/Main.coffee
@@ -13,21 +13,6 @@ Main =
           $.ready -> Captcha.fixes.init()
       return
 
-    # Disrupt loading of ads from malicious/irresponsible providers.
-    $.global ->
-      nuke = (obj, prop) ->
-        try
-          Object.defineProperty obj, prop,
-            configurable: false
-            get: -> throw new Error()
-            set: -> throw new Error()
-      for prop in ['atOptions', 'adsterra_key', 'EpmadsConfig', 'epmads_key', 'EpomConfig', 'epom_key', 'exoDocumentProtocol', 'supp_key']
-        nuke window, prop
-      return
-    $.on window, 'beforescriptexecute', (e) ->
-      host = e.target.src.split('/')[2]?.match(/[^.]+\.[^.]+$/)?[0]
-      e.preventDefault() if host in ['bnhtml.com', 'ecpmrocks.com', 'advertisation.com', 'exoclick.com', 'n298adserv.com']
-
     # Detect multiple copies of 4chan X
     $.on d, '4chanXInitFinished', ->
       if Main.expectInitFinished
@@ -61,11 +46,35 @@ Main =
     Conf['JSON Navigation'] = true
     Conf['Oekaki Links'] = true
 
+    # Pseudo-enforce default whitelist while configuration loads
+    $.global ->
+      {whitelist} = document.currentScript.dataset
+      whitelist = whitelist.split('\n').filter (x) -> x[0] isnt "'"
+      oldFun = {}
+      for key in ['createElement', 'write']
+        oldFun[key] = document[key]
+        document[key] = do (key) -> (arg) ->
+          s = document.currentScript
+          if s and s.src and whitelist.indexOf(s.src.split('/')[..2].join('/')) < 0
+            throw Error()
+          oldFun[key].call document, arg
+      document.addEventListener 'csp-ready', ->
+        document[key] = oldFun[key] for key of oldFun
+      , false
+    ,
+      whitelist: Conf['jsWhitelist']
+
     # Get saved values as items
     items = {}
     items[key] = undefined for key of Conf
     items['previousversion'] = undefined
     $.get items, (items) ->
+
+      # Enforce JS whitelist
+      jsWhitelist = items['jsWhitelist'] ? Conf['jsWhitelist']
+      $.addCSP "script-src #{jsWhitelist.replace(/[\s;]+/g, ' ')}"
+      $.event 'csp-ready'
+
       $.asap docSet, ->
 
         # Don't hide the local storage warning behind a settings panel.
diff --git a/src/platform/$.coffee b/src/platform/$.coffee
index 12087bb12..d2f130701 100644
--- a/src/platform/$.coffee
+++ b/src/platform/$.coffee
@@ -138,6 +138,18 @@ $.addStyle = (css, id, test='head') ->
     $.add d.head, style
   style
 
+$.addCSP = (policy) ->
+  meta = $.el 'meta',
+    httpEquiv: 'Content-Security-Policy'
+    content:   policy
+  if d.head
+    $.add d.head, meta
+    $.rm meta
+  else
+    head = $.add (doc or d), $.el('head')
+    $.add head, meta
+    $.rm head
+
 $.x = (path, root) ->
   root or= d.body
   # XPathResult.ANY_UNORDERED_NODE_TYPE === 8
@@ -296,15 +308,16 @@ $.queueTask = do ->
       taskQueue.push arguments
       setTimeout execTask, 0
 
-$.globalEval = (code) ->
+$.globalEval = (code, data) ->
   script = $.el 'script',
     textContent: code
+  $.extend script.dataset, data if data
   $.add (d.head or doc), script
   $.rm script
 
-$.global = (fn) ->
+$.global = (fn, data) ->
   if doc
-    $.globalEval "(#{fn})();"
+    $.globalEval "(#{fn})();", data
   else
     # XXX dwb
     fn()