diff --git a/caps/nsScriptSecurityManager.cpp b/caps/nsScriptSecurityManager.cpp
index 49fb4e7601b..febd4de1222 100644
--- a/caps/nsScriptSecurityManager.cpp
+++ b/caps/nsScriptSecurityManager.cpp
@@ -629,6 +629,42 @@ EqualOrSubdomain(nsIURI* aProbeArg, nsIURI* aBase)
     }
 }
 
+static bool
+AllSchemesMatch(nsIURI* aURI, nsIURI* aOtherURI)
+{
+    nsCOMPtr<nsINestedURI> nestedURI = do_QueryInterface(aURI);
+    nsCOMPtr<nsINestedURI> nestedOtherURI = do_QueryInterface(aOtherURI);
+    auto stringComparator = nsCaseInsensitiveCStringComparator();
+    if (!nestedURI && !nestedOtherURI) {
+        // Neither of the URIs is nested, compare their schemes directly:
+        nsAutoCString scheme, otherScheme;
+        aURI->GetScheme(scheme);
+        aOtherURI->GetScheme(otherScheme);
+        return scheme.Equals(otherScheme, stringComparator);
+    }
+    while (nestedURI && nestedOtherURI) {
+        nsCOMPtr<nsIURI> currentURI = do_QueryInterface(nestedURI);
+        nsCOMPtr<nsIURI> currentOtherURI = do_QueryInterface(nestedOtherURI);
+        nsAutoCString scheme, otherScheme;
+        currentURI->GetScheme(scheme);
+        currentOtherURI->GetScheme(otherScheme);
+        if (!scheme.Equals(otherScheme, stringComparator)) {
+            return false;
+        }
+
+        nestedURI->GetInnerURI(getter_AddRefs(currentURI));
+        nestedOtherURI->GetInnerURI(getter_AddRefs(currentOtherURI));
+        nestedURI = do_QueryInterface(currentURI);
+        nestedOtherURI = do_QueryInterface(currentOtherURI);
+    }
+    if (!!nestedURI != !!nestedOtherURI) {
+        // If only one of the scheme chains runs out at one point, clearly the chains
+        // aren't of the same length, so we bail:
+        return false;
+    }
+    return true;
+}
+
 NS_IMETHODIMP
 nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
                                                    nsIURI *aTargetURI,
@@ -729,14 +765,30 @@ nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
     rv = sourceBaseURI->GetScheme(sourceScheme);
     if (NS_FAILED(rv)) return rv;
 
+    // When comparing schemes, if the relevant pref is set, view-source URIs
+    // are reachable from same-protocol (so e.g. file: can link to
+    // view-source:file). This is required for reftests.
+    static bool sViewSourceReachableFromInner = false;
+    static bool sCachedViewSourcePref = false;
+    if (!sCachedViewSourcePref) {
+        sCachedViewSourcePref = true;
+        mozilla::Preferences::AddBoolVarCache(&sViewSourceReachableFromInner,
+            "security.view-source.reachable-from-inner-protocol");
+    }
+
+    bool targetIsViewSource = false;
+
     if (sourceScheme.LowerCaseEqualsLiteral(NS_NULLPRINCIPAL_SCHEME)) {
         // A null principal can target its own URI.
         if (sourceURI == aTargetURI) {
             return NS_OK;
         }
     }
-    else if (targetScheme.Equals(sourceScheme,
-                                 nsCaseInsensitiveCStringComparator()))
+    else if (AllSchemesMatch(sourceURI, aTargetURI) ||
+             (sViewSourceReachableFromInner &&
+              sourceScheme.EqualsIgnoreCase(targetScheme.get()) &&
+              NS_SUCCEEDED(aTargetURI->SchemeIs("view-source", &targetIsViewSource)) &&
+              targetIsViewSource))
     {
         // every scheme can access another URI from the same scheme,
         // as long as they don't represent null principals...
@@ -785,7 +837,7 @@ nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
     // at the flags for our one URI.
 
     // Check for system target URI
-    rv = DenyAccessIfURIHasFlags(targetBaseURI,
+    rv = DenyAccessIfURIHasFlags(aTargetURI,
                                  nsIProtocolHandler::URI_DANGEROUS_TO_LOAD);
     if (NS_FAILED(rv)) {
         // Deny access, since the origin principal is not system
@@ -853,7 +905,7 @@ nsScriptSecurityManager::CheckLoadURIWithPrincipal(nsIPrincipal* aPrincipal,
     }
 
     // Check for target URI pointing to a file
-    rv = NS_URIChainHasFlags(targetBaseURI,
+    rv = NS_URIChainHasFlags(aTargetURI,
                              nsIProtocolHandler::URI_IS_LOCAL_FILE,
                              &hasFlags);
     NS_ENSURE_SUCCESS(rv, rv);
@@ -1639,3 +1691,4 @@ nsScriptSecurityManager::PolicyAllowsScript(nsIURI* aURI, bool *aRv)
 
     return NS_OK;
 }
+
diff --git a/layout/tools/reftest/reftest-preferences.js b/layout/tools/reftest/reftest-preferences.js
index ecf2ab111fe..bfc1569ae9f 100644
--- a/layout/tools/reftest/reftest-preferences.js
+++ b/layout/tools/reftest/reftest-preferences.js
@@ -64,3 +64,7 @@
 
     // Allow XUL and XBL files to be opened from file:// URIs
     branch.setBoolPref("dom.allow_XUL_XBL_for_file", true);
+
+    // Allow view-source URIs to be opened from URIs that share
+    // their protocol with the inner URI of the view-source URI
+    branch.setBoolPref("security.view-source.reachable-from-inner-protocol", true);
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 8f8c822188e..274ac474d18 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2025,6 +2025,10 @@ pref("security.cert_pinning.enforcement_level", 0);
 // for tests.
 pref("security.cert_pinning.process_headers_from_non_builtin_roots", false);
 
+// If set to true, allow view-source URIs to be opened from URIs that share
+// their protocol with the inner URI of the view-source URI
+pref("security.view-source.reachable-from-inner-protocol", false);
+
 // Modifier key prefs: default to Windows settings,
 // menu access key = alt, accelerator key = control.
 // Use 17 for Ctrl, 18 for Alt, 224 for Meta, 91 for Win, 0 for none. Mac settings in macprefs.js
diff --git a/netwerk/protocol/about/nsAboutProtocolHandler.cpp b/netwerk/protocol/about/nsAboutProtocolHandler.cpp
index 70536345a12..91664952e0c 100644
--- a/netwerk/protocol/about/nsAboutProtocolHandler.cpp
+++ b/netwerk/protocol/about/nsAboutProtocolHandler.cpp
@@ -39,7 +39,8 @@ static bool IsSafeToLinkForUntrustedContent(nsIAboutModule *aModule, nsIURI *aUR
 }
 ////////////////////////////////////////////////////////////////////////////////
 
-NS_IMPL_ISUPPORTS(nsAboutProtocolHandler, nsIProtocolHandler, nsISupportsWeakReference)
+NS_IMPL_ISUPPORTS(nsAboutProtocolHandler, nsIProtocolHandler,
+    nsIProtocolHandlerWithDynamicFlags, nsISupportsWeakReference)
 
 ////////////////////////////////////////////////////////////////////////////////
 // nsIProtocolHandler methods:
@@ -65,6 +66,33 @@ nsAboutProtocolHandler::GetProtocolFlags(uint32_t *result)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsAboutProtocolHandler::GetFlagsForURI(nsIURI* aURI, uint32_t* aFlags)
+{
+    // First use the default (which is "unsafe for content"):
+    GetProtocolFlags(aFlags);
+
+    // Now try to see if this URI overrides the default:
+    nsCOMPtr<nsIAboutModule> aboutMod;
+    nsresult rv = NS_GetAboutModule(aURI, getter_AddRefs(aboutMod));
+    if (NS_FAILED(rv)) {
+      // Swallow this and just tell the consumer the default:
+      return NS_OK;
+    }
+    uint32_t aboutModuleFlags = 0;
+    rv = aboutMod->GetURIFlags(aURI, &aboutModuleFlags);
+    // This should never happen, so pass back the error:
+    NS_ENSURE_SUCCESS(rv, rv);
+
+    // If marked as safe, and not marked unlinkable, pass 'safe' flags.
+    if ((aboutModuleFlags & nsIAboutModule::URI_SAFE_FOR_UNTRUSTED_CONTENT) &&
+        !(aboutModuleFlags & nsIAboutModule::MAKE_UNLINKABLE)) {
+        *aFlags = URI_NORELATIVE | URI_NOAUTH | URI_LOADABLE_BY_ANYONE |
+            URI_SAFE_TO_LOAD_IN_SECURE_CONTEXT;
+    }
+    return NS_OK;
+}
+
 NS_IMETHODIMP
 nsAboutProtocolHandler::NewURI(const nsACString &aSpec,
                                const char *aCharset, // ignore charset info
diff --git a/netwerk/protocol/about/nsAboutProtocolHandler.h b/netwerk/protocol/about/nsAboutProtocolHandler.h
index 007975ad46d..f3e9e19291a 100644
--- a/netwerk/protocol/about/nsAboutProtocolHandler.h
+++ b/netwerk/protocol/about/nsAboutProtocolHandler.h
@@ -13,7 +13,8 @@
 
 class nsIURI;
 
-class nsAboutProtocolHandler : public nsIProtocolHandler
+class nsAboutProtocolHandler : public nsIProtocolHandlerWithDynamicFlags
+                             , public nsIProtocolHandler
                              , public nsSupportsWeakReference
 {
 public:
@@ -21,6 +22,7 @@ public:
 
     // nsIProtocolHandler methods:
     NS_DECL_NSIPROTOCOLHANDLER
+    NS_DECL_NSIPROTOCOLHANDLERWITHDYNAMICFLAGS
 
     // nsAboutProtocolHandler methods:
     nsAboutProtocolHandler() {}
diff --git a/netwerk/protocol/viewsource/nsViewSourceHandler.cpp b/netwerk/protocol/viewsource/nsViewSourceHandler.cpp
index 5f8932b50e8..b346c2e900f 100644
--- a/netwerk/protocol/viewsource/nsViewSourceHandler.cpp
+++ b/netwerk/protocol/viewsource/nsViewSourceHandler.cpp
@@ -35,7 +35,7 @@ nsViewSourceHandler::GetDefaultPort(int32_t *result)
 NS_IMETHODIMP
 nsViewSourceHandler::GetProtocolFlags(uint32_t *result)
 {
-    *result = URI_NORELATIVE | URI_NOAUTH | URI_LOADABLE_BY_ANYONE |
+    *result = URI_NORELATIVE | URI_NOAUTH | URI_DANGEROUS_TO_LOAD |
         URI_NON_PERSISTABLE;
     return NS_OK;
 }
diff --git a/netwerk/test/mochitests/mochitest.ini b/netwerk/test/mochitests/mochitest.ini
index da5a4f8acb7..d7e984618ee 100644
--- a/netwerk/test/mochitests/mochitest.ini
+++ b/netwerk/test/mochitests/mochitest.ini
@@ -25,6 +25,7 @@ skip-if = e10s
 [test_user_agent_updates.html]
 skip-if = e10s
 [test_user_agent_updates_reset.html]
+[test_viewsource_unlinkable.html]
 [test_xhr_method_case.html]
 [test_signed_web_packaged_app.html]
 skip-if = e10s || buildapp != 'browser'
diff --git a/netwerk/test/mochitests/test_viewsource_unlinkable.html b/netwerk/test/mochitests/test_viewsource_unlinkable.html
new file mode 100644
index 00000000000..9a1a35d682d
--- /dev/null
+++ b/netwerk/test/mochitests/test_viewsource_unlinkable.html
@@ -0,0 +1,27 @@
+<!DOCTYPE HTML>
+<html>
+<!--
+-->
+<head>
+  <title>Test for view-source linkability</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+
+<script type="text/javascript">
+function runTest() {
+  SimpleTest.doesThrow(function() {
+    window.open('view-source:' + location.href, "_blank");
+  }, "Trying to access view-source URL from unprivileged code should throw.");
+  SimpleTest.finish();
+}
+</script>
+</head>
+<body onload="runTest();">
+<p id="display"></p>
+<div id="content" style="display: none"></div>
+<pre id="test">
+</pre>
+</body>
+</html>
+
+