open yahoo.com via UK proxy start selecting content with mouse from top to bottom till autoscroll starts. The WebView crashes with the following dump.
The bug is reproduced easily though not every time and not on every site content (that's why the specific proxy required)

C [jfxwebkit.dll+0x127cc30] JNIEnv_::GetPrimitiveArrayCritical+0x20
C [jfxwebkit.dll+0x127f5e1] WebCore::Font::selectionRectForComplexText+0x1a1
C [jfxwebkit.dll+0x121bbaa] WebCore::Font::selectionRectForText+0xba
C [jfxwebkit.dll+0x124cdd2] WebCore::GraphicsContext::drawHighlightForText+0x42
C [jfxwebkit.dll+0x13c3b06] WebCore::InlineTextBox::paintSelection+0x446
C [jfxwebkit.dll+0x13c0b73] WebCore::InlineTextBox::paint+0xa13
C [jfxwebkit.dll+0x13b360e] WebCore::InlineFlowBox::paint+0x31e
C [jfxwebkit.dll+0x15d56f8] WebCore::RootInlineBox::paint+0x48
C [jfxwebkit.dll+0x15281e5] WebCore::RenderLineBoxList::paint+0x425
C [jfxwebkit.dll+0x1411b2e] WebCore::RenderBlockFlow::paintInlineChildren+0x7e
C [jfxwebkit.dll+0x13e021c] WebCore::RenderBlock::paintContents+0x5c
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x158391d] WebCore::RenderTableCell::paint+0x3d
C [jfxwebkit.dll+0x1590fb6] WebCore::RenderTableSection::paintCell+0x116
C [jfxwebkit.dll+0x159148a] WebCore::RenderTableSection::paintObject+0x4ca
C [jfxwebkit.dll+0x1590a6e] WebCore::RenderTableSection::paint+0x9e
C [jfxwebkit.dll+0x157a386] WebCore::RenderTable::paintObject+0x166
C [jfxwebkit.dll+0x157a1f5] WebCore::RenderTable::paint+0xc5
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x13dafe5] WebCore::RenderBlock::paintChild+0x245
C [jfxwebkit.dll+0x13dad84] WebCore::RenderBlock::paintChildren+0x44
C [jfxwebkit.dll+0x13e02d0] WebCore::RenderBlock::paintContents+0x110
C [jfxwebkit.dll+0x13daabd] WebCore::RenderBlock::paintObject+0x1fd
C [jfxwebkit.dll+0x13da811] WebCore::RenderBlock::paint+0x101
C [jfxwebkit.dll+0x14e7466] WebCore::RenderLayer::paintForegroundForFragmentsWithPhase+0x186
C [jfxwebkit.dll+0x14e71ec] WebCore::RenderLayer::paintForegroundForFragments+0x1cc
C [jfxwebkit.dll+0x14e5d98] WebCore::RenderLayer::paintLayerContents+0x778
C [jfxwebkit.dll+0x14e53fe] WebCore::RenderLayer::paintLayerContentsAndReflection+0xce
C [jfxwebkit.dll+0x14e51ec] WebCore::RenderLayer::paintLayer+0x4fc
C [jfxwebkit.dll+0x14e613e] WebCore::RenderLayer::paintList+0xbe
C [jfxwebkit.dll+0x14e5e35] WebCore::RenderLayer::paintLayerContents+0x815
C [jfxwebkit.dll+0x14e53fe] WebCore::RenderLayer::paintLayerContentsAndReflection+0xce
C [jfxwebkit.dll+0x14e51ec] WebCore::RenderLayer::paintLayer+0x4fc
C [jfxwebkit.dll+0x14e613e] WebCore::RenderLayer::paintList+0xbe
C [jfxwebkit.dll+0x14e5e35] WebCore::RenderLayer::paintLayerContents+0x815
C [jfxwebkit.dll+0x14e53fe] WebCore::RenderLayer::paintLayerContentsAndReflection+0xce
C [jfxwebkit.dll+0x14e51ec] WebCore::RenderLayer::paintLayer+0x4fc
C [jfxwebkit.dll+0x14e613e] WebCore::RenderLayer::paintList+0xbe
C [jfxwebkit.dll+0x14e5e35] WebCore::RenderLayer::paintLayerContents+0x815
C [jfxwebkit.dll+0x14e53fe] WebCore::RenderLayer::paintLayerContentsAndReflection+0xce
C [jfxwebkit.dll+0x14e51ec] WebCore::RenderLayer::paintLayer+0x4fc
C [jfxwebkit.dll+0x14de9e6] WebCore::RenderLayer::paint+0x96
C [jfxwebkit.dll+0x1175d60] WebCore::FrameView::paintContents+0x3a0
C [jfxwebkit.dll+0x1330ac9] WebCore::ScrollView::paint+0x229
C [jfxwebkit.dll+0x12e0352] WebCore::WebPage::paintContents+0x52
C [jfxwebkit.dll+0x12553b2] WebCore::GraphicsLayer::paintGraphicsLayerContents+0xa2
C [jfxwebkit.dll+0x1699375] WebCore::BitmapTextureImageBuffer::updateContents+0xc5
C [jfxwebkit.dll+0x169e7fe] WebCore::TextureMapperTile::updateContents+0x14e
C [jfxwebkit.dll+0x169ef81] WebCore::TextureMapperTiledBackingStore::updateContents+0x71
C [jfxwebkit.dll+0x1690e29] WebCore::GraphicsLayerTextureMapper::updateBackingStoreIfNeeded+0x139
C [jfxwebkit.dll+0x1690274] WebCore::GraphicsLayerTextureMapper::flushCompositingStateForThisLayerOnly+0x34
C [jfxwebkit.dll+0x12e004b] WebCore::WebPage::syncLayers+0x6b
C [jfxwebkit.dll+0x12def63] WebCore::WebPage::prePaint+0x33
C [jfxwebkit.dll+0x12e1f4a] Java_com_sun_webkit_WebPage_twkPrePaint+0x1a

java.lang.StringIndexOutOfBoundsException: String index out of range: 14
at java.lang.String.substring(String.java:1963)
at com.sun.webkit.WebPage.twkPrePaint(Native Method)
at com.sun.webkit.WebPage.updateDirty(WebPage.java:266)
at com.sun.webkit.WebPage.updateContent(WebPage.java:592)
at com.sun.javafx.sg.prism.web.NGWebView.update(NGWebView.java:74)
at javafx.scene.web.WebView.handleStagePulse(WebView.java:978)
at javafx.scene.web.WebView.lambda$new$29(WebView.java:278)
at com.sun.javafx.tk.Toolkit.lambda$runPulse$31(Toolkit.java:339)
at java.security.AccessController.doPrivileged(Native Method)
at com.sun.javafx.tk.Toolkit.runPulse(Toolkit.java:338)
at com.sun.javafx.tk.Toolkit.firePulse(Toolkit.java:362)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:510)
at com.sun.javafx.tk.quantum.QuantumToolkit.pulse(QuantumToolkit.java:490)
at com.sun.javafx.tk.quantum.QuantumToolkit.lambda$runToolkit$401(QuantumToolkit.java:319)
at com.sun.glass.ui.InvokeLaterDispatcher$Future.run(InvokeLaterDispatcher.java:95)
at com.sun.glass.ui.win.WinApplication._runLoop(Native Method)
at com.sun.glass.ui.win.WinApplication.lambda$null$146(WinApplication.java:108)
at java.lang.Thread.run(Thread.java:745)