It was working earlier, and on upgrade on ubuntu packages (apt-get upgrade), jenkins have got upgraded to 1.629 and I find all my jobs which were publishing html file, the html viewer is broken and even the shown zip link doesn't work (refer screenshot)
+ even the saved HTML in build artifact doesn't open with proper html, css. it opens vim like ugly style.
Very Strange thing to note:
even the confix.xml used to say <version>1.629</version> before upgrade and saya the same now as well but yes I can find the difference in Jenkins UI to say that its upgraded (its tabbed UI like jenkins 2 though I get notification to upgrade it to jenkins 2)

Is upgrading to 2 is only solution or will it make worse?