Bug 1346720 - Disallow invalid report IDs early on. r=gerald

MozReview-Commit-ID: GBDnzYh0gPt

browser/base/content/browser-media.js

@@ -249,6 +249,10 @@ let gDecoderDoctorHandler = {
     //   resolution of that issue, to be reported as telemetry.
     let {type, isSolved, decoderDoctorReportId, formats} = parsedData;
     type = type.toLowerCase();
+    // Error out early on invalid ReportId
+    if (!(/^\w+$/mi).test(decoderDoctorReportId)) {
+      return
+    }
     let title = gDecoderDoctorHandler.getLabelForNotificationBox(type);
     if (!title) {
       return;

dom/media/DecoderDoctorDiagnostics.cpp

@@ -247,6 +247,7 @@ DecoderDoctorDocumentWatcher::EnsureTimerIsStarted()
   }
 }
 
+// Note: ReportStringIds are limited to alphanumeric only.
 static const NotificationAndReportStringId sMediaWidevineNoWMF=
   { dom::DecoderDoctorNotificationType::Platform_decoder_not_found,
     "MediaWidevineNoWMF" };