CSS resources prefetching as a mitigation against CSS PP0 (https://github.com/Yossioren/pp0).

src/content/content.js

@@ -178,6 +178,15 @@ ns.on("capabilities", () => {
   notifyPage();
 });
 
+prefetchCSSResources(false, (rule, url) => {
+  debug("Prefetching %s from CSS", url, rule.cssText);
+  /* Uncomment to debug prefetching by prefixing the prefetched domains
+  url.hostname = `prefetch.${url.hostname}`;
+  new Image().src = url;
+  return true;
+  */
+});
+
 ns.fetchPolicy();
 notifyPage();
 

src/manifest.json

@@ -103,6 +103,7 @@
         "nscl/common/RequestKey.js",
         "content/DocumentCSP.js",
         "nscl/content/NoscriptElements.js",
+        "/nscl/content/prefetchCSSResources.js",
         "content/onScriptDisabled.js",
         "content/staticNS.js",
         "content/PlaceHolder.js",

src/nscl

@@ -1 +1 @@
-Subproject commit b222a9fdb06ff5ae5049aeeee32dcc83a4ef4c2a
+Subproject commit 7ec0758e425af9676466fe5f537b65b7998d4823