Why might weird characters ($p) appear at beginning of every file in vim?

Question

Every file I open in vim lately, even new empty files, as a ($p) at the beginning. This does not appear to be real - inserting text overwrites it, and once it's overwritten it does not return.

I have no idea what might be doing this, or how to fix it.

Answer 1

Fixed: I resolved this issue on OSX 10.13.4 by updating to iTerm2 3.1.5

vim github issue #2008 reveals it's your terminal emulator not supporting certain DCS (Device Control Strings)

https://github.com/vim/vim/issues/2008

Works for me with version combination:

VIM version 8.0.1283

iTerm2 3.1.15

OSX 10.13.4