I am referring to the grey background highlighting which is making vim unreadable. Note - I am running vim on Windows Subsystem for Linux. Also, this is not search highlighting. This is the default view every time I open Vim.
It seems it has nothing to do with syntax highlighting. I created a new file named a.txt . On using :syn list , it said no syntax items defined for this buffer, but I still had grey background on every line.
It seems that my default colorscheme - 'evening' had been modified by the last windows update. A workaround is to change the colorscheme to different value - desert/elflord etc seem to be working fine. Note - this is not a solution just a workaround , as you can see there is still grey background highlighting in the top rows.