(IANAL) Seems to be that yeah, GitHub should have known. I'd recommend going to the complaint[1] and skipping the news article. So, the complaint states[1],

> This outside individual (“the hacker”) posted this Personal Information on GitHub.com, GitHub’s website, which encourages (at least friendly) hacking and which is publicly available. As a result of GitHub’s failure to monitor, remove, or otherwise recognize and act upon obviously-hacked data that was displayed, disclosed, and used on and by GitHub and its website, the Personal Information sat on GitHub.com for nearly three months.

First, I do not like that the lawyers are punning between hacker "a person who uses computers to gain unauthorized access to data" ("the hacker") and hacker "an enthusiastic and skillful computer programmer or user" ("GitHub's website, which encourages […] hacking").

They allege it was the actual data posted:

> Not surprisingly, therefore, the hacker, a software developer, posted the breached data on
GitHub.com

This part is interesting:

> According to the timestamp on the file containing certain Capital One customers’ breached data, the hacker posted the data on GitHub.com on or about April 21, 2019.

Because AFAIK, GitHub does not display upload times on its website, so I'm curious how the plaintiffs came to this conclusion. IIRC, the times that GitHub displays, e.g., in its listing of files are the times in the git data, which do not necessarily reflect the time the data was first uploaded to GitHub. (E.g., compare that a commit has a commit timestamp, but you can commit, wait 2 days, and then upload the commit to GitHub.)

> Nevertheless, Capital One did not even begin to investigate the data breach until or
around July 17, 2019, when it received an email apparently from a GitHub.com user alerting Capital
One that there “appear[ed] to be some leaked” customer data publicly available on GitHub.com.

> GitHub, meanwhile, never alerted any victims that their highly sensitive Personal Information—including Social Security numbers—was displayed on its site, GitHub.com. Nor did GitHub timely remove the obviously hacked data. Instead, the hacked data was available on GitHub.com for three months.

> 22. GitHub apparently did not even suspend the hacker’s GitHub account or access to the
site, even though it knew or should have known that the hacker had breached GitHub’s own Terms of
Service, which state that: “GitHub has the right to suspend or terminate [a user’s] access to all or any
part of the [GitHub.com] Website at any time, with or without cause, with or without notice, effective
immediately.”

It seems likely that GitHub wasn't aware. Nowhere in the complaint do I see where GitHub is made aware of this issue prior to it being public.

This part is interesting:

> 28. GitHub had an obligation, under California law, to keep off (or to remove from) its site Social Security numbers and other Personal Information.

> 29. Further, pursuant to established industry standards, GitHub had an obligation to keep off (or to remove from) its site Social Security numbers and other Personal Information.

I don't know if "established industry standards" holds up in court, but the 28 there is interesting. Lawyers writing this complaint, y u no cite what part of CA law? CA's law is actually really easy to browse/lookup if you know what code and what section you're looking for.

[1]: https://www.dropbox.com/s/cjdflk7rh4z8ery/TZ_GitHub_CapitalO...