Ditto here, I've seen an unprecedented number of Firefox crashes in the first two hours of Fedora 25. Here's one that I can reproduce nearly every time, both with firefox-50.0-1.fc25.x86_64 and firefox-50.0.2-1.fc25.x86_64.rpm from koji:

- Go to https://bugzilla.redhat.com/show_bug.cgi?id=1163899
- Press end, press home -> crash (sometimes you need to repeat this a few times)
- Also sometimes happens with page up reaching top of the page

Here's a traceback of the above crash:
Thread 1 "firefox" received signal SIGTRAP, Trace/breakpoint trap.
_g_log_abort (breakpoint=breakpoint@entry=1) at gmessages.c:487
487     }
(gdb) bt
#0  0x00007f969eb21a21 in _g_log_abort (breakpoint=breakpoint@entry=1)
    at gmessages.c:487
#1  0x00007f969eb24161 in g_log_writer_default (log_level=6,
    log_level@entry=G_LOG_LEVEL_ERROR, fields=fields@entry=0x7ffe2fcb3800, n_fields=n_fields@entry=6, user_data=user_data@entry=0x0) at gmessages.c:2382
#2  0x00007f969eb225bc in g_log_structured_array (log_level=G_LOG_LEVEL_ERROR, fields=0x7ffe2fcb3800, n_fields=6) at gmessages.c:1770
#3  0x00007f969eb228b9 in g_log_structured (log_domain=log_domain@entry=0x7f96a1513cce "Gdk", log_level=log_level@entry=G_LOG_LEVEL_ERROR) at gmessages.c:1597
#4  0x00007f96a14d5e1e in _gdk_x11_display_error_event (display=display@entry=0x7f96868061c0 [GdkX11Display], error=error@entry=0x7ffe2fcb3f80)
    at gdkdisplay-x11.c:2579
#5  0x00007f96a14e2ff3 in gdk_x_error (xdisplay=
    0x7f96a25f6000, error=0x7ffe2fcb3f80) at gdkmain-x11.c:307
#6  0x00007f96a0d6aded in _XError (dpy=dpy@entry=0x7f96a25f6000, rep=rep@entry=0x7f965496e970) at XlibInt.c:1434
#7  0x00007f96a0d67d17 in handle_error (dpy=0x7f96a25f6000, err=0x7f965496e970, in_XReply=<optimized out>) at xcb_io.c:199
#8  0x00007f96a0d67dd5 in handle_response (dpy=dpy@entry=0x7f96a25f6000, response=0x7f965496e970, in_XReply=in_XReply@entry=0) at xcb_io.c:311
#9  0x00007f96a0d686d5 in _XEventsQueued (dpy=dpy@entry=0x7f96a25f6000, mode=mode@entry=2) at xcb_io.c:350
#10 0x00007f96a0d5a3a7 in XPending (dpy=0x7f96a25f6000) at Pending.c:55
#11 0x00007f96a14dd56e in gdk_check_xpending (display=0x7f96868061c0 [GdkX11Display]) at gdkeventsource.c:269
#12 0x00007f96a14dd56e in gdk_event_source_prepare (source=<optimized out>, timeout=timeout@entry=0x7ffe2fcb4144) at gdkeventsource.c:287
#13 0x00007f969eb1b699 in g_main_context_prepare (context=context@entry=0x7f9686821740, priority=priority@entry=0x7ffe2fcb41d0) at gmain.c:3501
#14 0x00007f969eb1c07b in g_main_context_iterate (context=context@entry=0x7f9686821740, block=block@entry=0, dispatch=dispatch@entry=1, self=<optimized out>)
    at gmain.c:3909
#15 0x00007f969eb1c26c in g_main_context_iteration (context=0x7f9686821740,
    context@entry=0x0, may_block=0) at gmain.c:3990
---Type <return> to continue, or q <return> to quit---
#16 0x00007f9694b3585f in nsAppShell::ProcessNextNativeEvent(bool) (this=<optimized out>, mayWait=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/widget/gtk/nsAppShell.cpp:270
#17 0x00007f9694b1d4b3 in nsBaseAppShell::DoProcessNextNativeEvent(bool) (this=this@entry=0x7f967e307140, mayWait=mayWait@entry=false)
    at /usr/src/debug/firefox-50.0/firefox-50.0/widget/nsBaseAppShell.cpp:138
#18 0x00007f9694b1d612 in nsBaseAppShell::OnProcessNextEvent(nsIThreadInternal*, bool) (this=0x7f967e307140, thr=0x7f96a2569050, mayWait=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/widget/nsBaseAppShell.cpp:271
#19 0x00007f9693799b9f in nsThread::ProcessNextEvent(bool, bool*) (this=0x7f96a2569050, aMayWait=<optimized out>, aResult=0x7ffe2fcb4367)
    at /usr/src/debug/firefox-50.0/firefox-50.0/xpcom/threads/nsThread.cpp:1047
#20 0x00007f96937b4c37 in NS_ProcessNextEvent(nsIThread*, bool) (aThread=<optimized out>, aMayWait=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/xpcom/glue/nsThreadUtils.cpp:290
#21 0x00007f96939c371e in mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) (this=0x7f9686861e40, aDelegate=0x7f96a25ac840)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/glue/MessagePump.cpp:100
#22 0x00007f96939ae7a2 in MessageLoop::RunHandler() (this=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/chromium/src/base/message_loop.cc:225
#23 0x00007f96939ae7a2 in MessageLoop::Run() (this=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/chromium/src/base/message_loop.cc:205
#24 0x00007f9694b1b39c in nsBaseAppShell::Run() (this=0x7f967e307140)
    at /usr/src/debug/firefox-50.0/firefox-50.0/widget/nsBaseAppShell.cpp:156
#25 0x00007f969516ed12 in nsAppStartup::Run() (this=0x7f967e312060)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/components/startup/nsAppStartup.cpp:284
#26 0x00007f96951b3b78 in XREMain::XRE_mainRun() (this=this@entry=
    0x7ffe2fcb45f8)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4297
---Type <return> to continue, or q <return> to quit---
#27 0x00007f96951b3e3f in XREMain::XRE_main(int, char**, nsXREAppData const*) (this=this@entry=0x7ffe2fcb45f8, argc=argc@entry=2, argv=argv@entry=0x7ffe2fcb59d8, aAppData=aAppData@entry=0x7ffe2fcb47f8)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4424
#28 0x00007f96951b4080 in XRE_main(int, char**, nsXREAppData const*, uint32_t) (argc=2, argv=0x7ffe2fcb59d8, aAppData=0x7ffe2fcb47f8, aFlags=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4515
#29 0x000055cce145025e in do_main(int, char**, char**, nsIFile*) (argc=2, argv=0x7ffe2fcb59d8, envp=<optimized out>, xreDirectory=0x7f96a259ea80)
    at /usr/src/debug/firefox-50.0/firefox-50.0/browser/app/nsBrowserApp.cpp:247
#30 0x000055cce144f817 in main(int, char**, char**) (argc=2, argv=0x7ffe2fcb59d8, envp=0x7ffe2fcb59f0)
    at /usr/src/debug/firefox-50.0/firefox-50.0/browser/app/nsBrowserApp.cpp:380
(gdb)

Also got a one-time crash when clicking on save file on the attachment in https://bugzilla.redhat.com/show_bug.cgi?id=1399646#c1 but no traceback of that unfortunately.

Disabling smooth scrolling seems to prevent the above home-end-crash reproducer from happening. I'm still seeing other crashes though, such as this when just clicking on https://bugzilla.redhat.com/show_bug.cgi?id=1163899:


#0  0x00007f030f321a21 in _g_log_abort (breakpoint=breakpoint@entry=1)
    at gmessages.c:487
#1  0x00007f030f324161 in g_log_writer_default (log_level=6,
    log_level@entry=G_LOG_LEVEL_ERROR, fields=fields@entry=0x7ffc01354750, n_fields=n_fields@entry=6, user_data=user_data@entry=0x0) at gmessages.c:2382
#2  0x00007f030f3225bc in g_log_structured_array (log_level=G_LOG_LEVEL_ERROR, fields=0x7ffc01354750, n_fields=6) at gmessages.c:1770
#3  0x00007f030f3228b9 in g_log_structured (log_domain=log_domain@entry=0x7f0311d13cce "Gdk", log_level=log_level@entry=G_LOG_LEVEL_ERROR) at gmessages.c:1597
#4  0x00007f0311cd5e1e in _gdk_x11_display_error_event (display=display@entry=0x7f02f70061c0 [GdkX11Display], error=error@entry=0x7ffc01354ed0)
    at gdkdisplay-x11.c:2579
#5  0x00007f0311ce2ff3 in gdk_x_error (xdisplay=
    0x7f0312df6000, error=0x7ffc01354ed0) at gdkmain-x11.c:307
#6  0x00007f031156aded in _XError (dpy=dpy@entry=0x7f0312df6000, rep=rep@entry=0x7f02d08c5d00) at XlibInt.c:1434
#7  0x00007f0311567d17 in handle_error (dpy=0x7f0312df6000, err=0x7f02d08c5d00, in_XReply=<optimized out>) at xcb_io.c:199
#8  0x00007f0311567dd5 in handle_response (dpy=dpy@entry=0x7f0312df6000, response=0x7f02d08c5d00, in_XReply=in_XReply@entry=0) at xcb_io.c:311
#9  0x00007f03115686d5 in _XEventsQueued (dpy=dpy@entry=0x7f0312df6000, mode=mode@entry=2) at xcb_io.c:350
10 0x00007f in mozilla::ipc::MessagePump::Run(base::MessagePump::Delegate*) (this=0x7f02f7061d80, aDelegate=0x7f0312dac840)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/glue/MessagePump.cpp:100
#24 0x00007f03041ae7a2 in MessageLoop::RunHandler() (this=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/chromium/src/base/message_loop.cc:225
#25 0x00007f03041ae7a2 in MessageLoop::Run() (this=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/ipc/chromium/src/base/message_loop.cc:205
#26 0x00007f030531b39c in nsBaseAppShell::Run() (this=0x7f02eeb07140)
    at /usr/src/debug/firefox-50.0/firefox-50.0/widget/nsBaseAppShell.cpp:156
#27 0x00007f030596ed12 in nsAppStartup::Run() (this=0x7f02eeb12060)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/components/startup/nsApp---Type <return> to continue, or q <return> to quit---
Startup.cpp:284
#28 0x00007f03059b3b78 in XREMain::XRE_mainRun() (this=this@entry=
    0x7ffc01355678)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4297
#29 0x00007f03059b3e3f in XREMain::XRE_main(int, char**, nsXREAppData const*) (this=this@entry=0x7ffc01355678, argc=argc@entry=1, argv=argv@entry=0x7ffc01356a58, aAppData=aAppData@entry=0x7ffc01355878)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4424
#30 0x00007f03059b4080 in XRE_main(int, char**, nsXREAppData const*, uint32_t) (argc=1, argv=0x7ffc01356a58, aAppData=0x7ffc01355878, aFlags=<optimized out>)
    at /usr/src/debug/firefox-50.0/firefox-50.0/toolkit/xre/nsAppRunner.cpp:4515
#31 0x000055e51677c25e in do_main(int, char**, char**, nsIFile*) (argc=1, argv=0x7ffc01356a58, envp=<optimized out>, xreDirectory=0x7f0312d9ea80)
    at /usr/src/debug/firefox-50.0/firefox-50.0/browser/app/nsBrowserApp.cpp:247
#32 0x000055e51677b817 in main(int, char**, char**) (argc=1, argv=0x7ffc01356a58, envp=0x7ffc01356a68)
    at /usr/src/debug/firefox-50.0/firefox-50.0/browser/app/nsBrowserApp.cpp:380

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