The people who say 'It's 100% wrong' or the equivalent are self-appointed arbiters. Here is a less arrogant stance given as long ago as 2005 on EnglishForums [tidied]:
"There/Here is" with plural subject: [is this] allowed?
Please help [me] to decide. Is it just a common mistake, that even
native English speakers make, or is it actually correct English? And
if so, when is it appropriate to use this form?
Thanks in advance
2nd January 2005
[It is] still considered ungrammatical by many, and you would be wise
to avoid [it] in careful writing. But the fact remains that the use of
'here/there is' (usually as 'here's/there's') with plural nouns is
extremely common-- and acceptable-- informally. I use them myself
frequently when I speak.
One might ask the prescriptivists whether they allow 'It's me' or 'It's us', as probably 99+% of natural speakers use them.