Simply put:
this is a weak password.
hunter2
Password security is an evergreen topic.
A while back someone tallied up the weakest passwords of 2016.
And every time a big website that stores passwords in plaintext gets its database leaked,
someone tallies the weak password rankings from the leak.
Things like 123456, letmein, password are typical weak passwords.hunter2 is also a weak password.
The meme originated from a conversation on IRC around 2004:
<Cthon98> Type your password in the chat box, and the system will automatically turn it into asterisks
<Cthon98> ********* see!
<AzureDiamond> hunter2
<AzureDiamond> I don't see asterisks
<Cthon98> <AzureDiamond> *******
<Cthon98> I see what you sent as the line above
<AzureDiamond> Whoa, really?
<Cthon98> Yep
<AzureDiamond> You hunter2 my hunter2 with hunter2
<AzureDiamond> haha, look isn't this string interesting
<Cthon98> lol yeah. So every time you type hunter2, I see *******
<AzureDiamond> That's so cool, I didn't know IRC automatically masks passwords
<Cthon98> Yes, no matter where you type hunter2, others see *******
<AzureDiamond> Awesome!
<AzureDiamond> Wait, how do you know my password?
<Cthon98> Uh, I just copied your *******, and what you see might be its original form hunter2
Represented as an emoji image, it looks like this:

In the new era, this kind of routine looks like this:(Today is Pony Ma’s birthday, forward your password to five groups and look at your avatar)

XKCD 936 also talks about password security:

So one Redditor also discovered that
the classmate who wrote the school administration website
also reads XKCD:

So overall,hunter2 is a meme about weak passwords.
I hope everyone’s passwords are very secure,
and related virtual assets are very secure too :)
Other
Nowadays, using a good password manager is a great choice.
If you find password managers too troublesome,
choosing a password with numbers, uppercase letters, lowercase letters, special characters, and 10+ characters is also a good choice.
However many websites don’t support special characters ORZ
And some websites limit the password length to be very short…
╮(╯▽╰)╭ If, next to the website’s login box,
they could write down the password rules they originally required at registration, that would be nice.