Found with m-c: BuildID=20180511140745 SourceStamp=4303d49c53931385892231969e40048f096b4d4c Not sure if this is s-s but I'll mark it as such until it is reviewed. Assertion failure: parsedPolicyStr.Find("default-src") >= 0 (about: page must contain a CSP including default-src), at src/dom/base/nsDocument.cpp:5385 #0 AssertContentPrivilegedAboutPageHasCSP(nsIURI*, nsIPrincipal*) src/dom/base/nsDocument.cpp:5384:3 #1 nsDocument::EndLoad() src/dom/base/nsDocument.cpp:5393:3 #2 nsHTMLDocument::EndLoad() src/dom/html/nsHTMLDocument.cpp:841:15 #3 nsXMLContentSink::DidBuildModel(bool) src/dom/xml/nsXMLContentSink.cpp:337:16 #4 nsParser::DidBuildModel(nsresult) src/parser/htmlparser/nsParser.cpp:491:37 #5 nsParser::Terminate() src/parser/htmlparser/nsParser.cpp:604:5 #6 nsParser::Tokenize(bool) src/parser/htmlparser/nsParser.cpp:1549:20 #7 nsParser::ResumeParse(bool, bool, bool) src/parser/htmlparser/nsParser.cpp:1056:41 #8 nsParser::OnStopRequest(nsIRequest*, nsISupports*, nsresult) src/parser/htmlparser/nsParser.cpp:1476:10 #9 nsDocumentOpenInfo::OnStopRequest(nsIRequest*, nsISupports*, nsresult) src/uriloader/base/nsURILoader.cpp:375:15 #10 nsJARChannel::OnStopRequest(nsIRequest*, nsISupports*, nsresult) src/modules/libjar/nsJARChannel.cpp:1151:20 #11 non-virtual thunk to nsJARChannel::OnStopRequest(nsIRequest*, nsISupports*, nsresult) src/modules/libjar/nsJARChannel.cpp #12 nsInputStreamPump::OnStateStop() src/netwerk/base/nsInputStreamPump.cpp:702:20 #13 nsInputStreamPump::OnInputStreamReady(nsIAsyncInputStream*) src/netwerk/base/nsInputStreamPump.cpp:432:25 #14 nsInputStreamReadyEvent::Run() src/xpcom/io/nsStreamUtils.cpp:102:20 #15 nsThread::ProcessNextEvent(bool, bool*) src/xpcom/threads/nsThread.cpp:1090:14 #16 NS_ProcessNextEvent(nsIThread*, bool) src/xpcom/threads/nsThreadUtils.cpp:519:10 #17 mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) src/ipc/glue/MessagePump.cpp:97:21 #18 MessageLoop::RunInternal() src/ipc/chromium/src/base/message_loop.cc:326:10 #19 MessageLoop::Run() src/ipc/chromium/src/base/message_loop.cc:299:3 #20 nsBaseAppShell::Run() src/widget/nsBaseAppShell.cpp:157:27 #21 XRE_RunAppShell() src/toolkit/xre/nsEmbedFunctions.cpp:893:22 #22 mozilla::ipc::MessagePumpForChildProcess::Run(base::MessagePump::Delegate*) src/ipc/glue/MessagePump.cpp:269:9 #23 MessageLoop::RunInternal() src/ipc/chromium/src/base/message_loop.cc:326:10 #24 MessageLoop::Run() src/ipc/chromium/src/base/message_loop.cc:299:3 #25 XRE_InitChildProcess(int, char**, XREChildData const*) src/toolkit/xre/nsEmbedFunctions.cpp:719:34 #26 content_process_main(mozilla::Bootstrap*, int, char**) src/browser/app/../../ipc/contentproc/plugin-container.cpp:50:30 #27 main src/browser/app/nsBrowserApp.cpp:282:18 #28 __libc_start_main /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291 #29 _start (firefox+0x423444)

This assertion is supposed to indicate a problem that needs to be fixed by the about: page author, but I don't see an about page in your testcase. There's an implied about:blank, but about:blank is (supposed to be) explicitly excluded from that warning.

:vino, I don't know what frameset uses, I would have thought about:blank (which would be whitelisted). Anyway, can you take a look please?

I will mark it as duplicate of bug 1457433 which contains failures and more information from test jobs.