diff --git a/docshell/base/nsDocShell.cpp b/docshell/base/nsDocShell.cpp
index 9cc2a9fb2..d01e9053f 100644
--- a/docshell/base/nsDocShell.cpp
+++ b/docshell/base/nsDocShell.cpp
@@ -10591,6 +10591,25 @@ nsDocShell::DoURILoad(nsIURI* aURI,
     triggeringPrincipal = nsContentUtils::GetSystemPrincipal();
   }
 
+  if (!inherit) {
+    // We can confidently assume this is a channel that does not inherit
+    // the principal, and thus does not have flags on the protocol that
+    // ask for it. If the load is for a data: URI, inherit the principal if
+    // the system principal initiated the load to maintain compatibility
+    // with addons, but warn the user as a penalty (TenFourFox issue 525).
+    bool isData = false;
+    rv = aURI->SchemeIs("data", &isData);
+    if (NS_SUCCEEDED(rv) && isData) {
+      if (nsContentUtils::IsSystemPrincipal(triggeringPrincipal)) {
+        fprintf(stderr,
+"Warning: TenFourFox enabling inherited principal for data: URI from system.\n"
+"Warning: Make sure you are using a minimum set of up-to-date addons.\n"
+        );
+        inherit = true;
+      }
+    }
+  }
+
   nsSecurityFlags securityFlags = nsILoadInfo::SEC_NORMAL;
   if (inherit) {
     securityFlags |= nsILoadInfo::SEC_FORCE_INHERIT_PRINCIPAL;
diff --git a/modules/libpref/init/all.js b/modules/libpref/init/all.js
index 6156e1f33..c6bcbe9d5 100644
--- a/modules/libpref/init/all.js
+++ b/modules/libpref/init/all.js
@@ -2008,8 +2008,8 @@ pref("security.cert_pinning.process_headers_from_non_builtin_roots", false);
 // a NullPrincipal as the security context.
 // Otherwise it will inherit the origin from parent node, this is the legacy
 // behavior of Firefox.
-// TenFourFox issue 525 -- hold until better chrome detection is working
-pref("security.data_uri.unique_opaque_origin", false);
+// See also TenFourFox issue 525 for a workaround for old-style addons.
+pref("security.data_uri.unique_opaque_origin", true);
 
 // Modifier key prefs: default to Windows settings,
 // menu access key = alt, accelerator key = control.
diff --git a/storage/mozStorageService.cpp b/storage/mozStorageService.cpp
index 7a7b1e5b9..811e49340 100644
--- a/storage/mozStorageService.cpp
+++ b/storage/mozStorageService.cpp
@@ -975,6 +975,12 @@ Service::Observe(nsISupports *, const char *aTopic, const char16_t *)
       getConnections(connections);
       for (uint32_t i = 0, n = connections.Length(); i < n; i++) {
         if (!connections[i]->isClosed()) {
+          // This seems to happen with uBlock origin ...
+          fprintf(stderr, "FATAL ERROR: Storage connections not closed! Bad add-on! %s:%i\n", __FILE__, __LINE__);
+#if __ppc__
+          // Drop into the debugger.
+          __asm__("trap\n");
+#endif
           MOZ_CRASH();
         }
       }