A political campaign group working to elect Democratic senators left a spreadsheet containing the email addresses of 6.2 million Americans’ on an exposed server.

Data breach researchers at security firm UpGuard found the data in late July, and traced the storage bucket back to a former staffer at the Democratic Senatorial Campaign Committee, an organization that seeks grassroots donations and contributions to help elect Democratic candidates to the U.S. Senate.

The researchers published shared their findings exclusively with TechCrunch and published their findings.

The spreadsheet was titled “EmailExcludeClinton.csv” and was found in a similarly named unprotected Amazon S3 bucket without a password.

The file was uploaded in 2010 — a year after former Democratic senator and presidential candidate Hillary Clinton, whom the data is believed to be named after, became secretary of state.

UpGuard said the data may be people “who had opted out or should otherwise be excluded” from the committee’s marketing.

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