It's still a built-in feature, that hasn't gone away. What if you use right-click > Open in New Tab? Any better luck?

Thank you for sharing your Firefox configuration data (to the right of your question: Question Details > More System Details). I couldn't help noticing the extra Flash player DLLs which may cause compatibility and security issues:

• Shockwave Flash 11.9 r900
• Shockwave Flash 12.0 r0
• Shockwave Flash 22.0 r0
• Shockwave Flash 15.0 r0
• Shockwave Flash 14.0 r0
• Shockwave Flash 19.0 r0

You can download a cleanup tool from Adobe to root out all the various Flash versions, and then reinstall just the latest. Here are the links:

• Uninstaller:
  • https://helpx.adobe.com/flash-player/kb/uninstall-flash-player-windows.html
• Installer (either):
  • Standard installer (make sure to uncheck unwanted extras before downloading): https://get.adobe.com/flashplayer/
  • Full installers (first table, either EXE or MSI should work; you'll also need the ActiveX for IE if you use Flash in IE): https://www.adobe.com/products/flashplayer/distribution3.html

gillH said

'show all history' goes to the Library page. In the past if I clicked on a URL it opened in a new tab ,it no longer does this and I have to copy the URL ,open a new tab and paste it in the address bar. Have I got a setting wrong somewhere or is this no longer available?

Have tried the right click option and nothing happens .I will try the uninstalling of the flash player at a later time as a bit nervous about what to do.!!

Sometimes extensions interfere with the context menu, but it's hard to determine which might be the culprit, if any.

Do you want to try updating to Firefox 48.0.1 to see whether that makes any difference? See: Update Firefox to the latest release.