That’s according to findings published by security researcher Bob Diachenko who located an open and unprotected MongoDB instance in late December which contained 202,730,434 “very detailed” records. The database was indexed in data search engines Binary Edge and Shodan, and was freely visible without a password or login. It was only made private after Diachenko released on Twitter information about its existence.

Diachenko, who is director of cyber risk research at Hacken, wasn’t able to match the database with a specific service, but he did locate a three-year-old GitHub repository for an app that included “identical structural patterns as those used in the exposed resumes.” Again, ownership is not clear at this point, although the records do seem to contain data that was scraped from Chinese classifieds, including the Craigslist-like 58.com.

A 58.com spokesperson denied that the records were its creation. They instead claimed that their service had been the victim of scraping from a third-party.

“We have searched all over the database of us and investigated all the other storage, turned out that the sample data is not leaked from us. It seems that the data is leaked from a third party who scrape[d] data from many CV websites,” a spokesperson told Diachenko.

TechCrunch contacted 58.com but we have not yet received a response.

While the database has now been secured, it was potentially vulnerable for up to three years and there’s already evidence that it had been regularly accessed. Although, again, it isn’t clear by whom.

“It’s worth noting that MongoDB log showed at least a dozen IPs who might have accessed the data before it was taken offline,” Diachenko wrote.

There’s plenty of mystery here — it isn’t clear whether 58.com was behind the hole, or if it is a rival service or a scraper — but what is more certain is that the vulnerability is one of the largest of its kind to be found in China.