I can't even see the Submit button below while entering this bug.
$ gtk-query-settings theme
                     gtk-theme-name: "HighContrast"
                gtk-icon-theme-name: "HighContrast"
!           gtk-fallback-icon-theme: NULL
                 gtk-key-theme-name: NULL
              gtk-cursor-theme-name: NULL
              gtk-cursor-theme-size: 0
               gtk-sound-theme-name: "freedesktop"
  gtk-application-prefer-dark-theme: FALSE
Package: epiphany-browser
Version: 3.22.7-1
-- System Information:
Debian Release: buster/sid
  APT prefers experimental
  APT policy: (990, 'experimental'), (500, 'unstable')
Architecture: i386 (i686)

Kernel: Linux 4.11.0-2-686-pae (SMP w/1 CPU core)
Locale: LANG=zh_TW.UTF-8, LC_CTYPE=zh_TW.UTF-8 (charmap=UTF-8), LANGUAGE=zh_TW.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash
Init: systemd (via /run/systemd/system)

Versions of packages epiphany-browser depends on:
ii  dbus-x11 [dbus-session-bus]  1.11.14-1
ii  epiphany-browser-data        3.22.7-1
ii  gsettings-desktop-schemas    3.24.0-1
ii  iso-codes                    3.75-1
ii  libavahi-client3             0.6.32-2
ii  libavahi-common3             0.6.32-2
ii  libavahi-gobject0            0.6.32-2
ii  libc6                        2.24-12
ii  libcairo2                    1.14.10-1
ii  libgcr-base-3-1              3.20.0-5.1
ii  libgcr-ui-3-1                3.20.0-5.1
ii  libgdk-pixbuf2.0-0           2.36.5-3
ii  libglib2.0-0                 2.53.4-1
ii  libgnome-desktop-3-12        3.22.2-1
ii  libgtk-3-0                   3.22.16-1
ii  libjavascriptcoregtk-4.0-18  2.17.4-1
ii  libnotify4                   0.7.7-2
ii  libpango-1.0-0               1.40.6-1
ii  libpangocairo-1.0-0          1.40.6-1
ii  libsecret-1-0                0.18.5-3.1
ii  libsoup2.4-1                 2.56.0-2
ii  libsqlite3-0                 3.19.3-3
ii  libwebkit2gtk-4.0-37         2.17.4-1
ii  libx11-6                     2:1.6.4-3
ii  libxml2                      2.9.4+dfsg1-3
ii  libxslt1.1                   1.1.29-2.1

Versions of packages epiphany-browser recommends:
pn  browser-plugin-evince  <none>
ii  ca-certificates        20161130+nmu1
pn  evince                 <none>
ii  yelp                   3.22.0-1

epiphany-browser suggests no packages.

-- no debconf information