The person or persons who identify as computer hacker "Guccifer 2.0" on Tuesday released what it said is a trove of documents supposedly stolen from the computer system of the Clinton Foundation, apparently including spreadsheets full of the contact information for Democratic donors, and other sensitive material. Guccifer has successfully hacked other U.S. political targets, including the Democratic National Committee, but this material has not been authenticated and the Clinton Foundation says the hacker's claims are not true.

No evidence of a #Guccifer hack at @ClintonFdn, no notification by law enforcement, and none of the files or folders shown are ours. — Donna E. Shalala (@DonnaShalala) October 4, 2016

“Many of you have been waiting for this, some even asked me to do it,” Guccifer 2.0 wrote on the blog normally used to distribute stolen material. “So, this is the moment. I hacked the Clinton Foundation server and downloaded hundreds of thousands of docs and donors’ databases.”

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He also mocked the security procedures of the Clinton family foundation, which has been the focus of relentless attacks by the opponents of Democratic presidential nominee Hillary Clinton. They claim that the foundation’s large network of international donors has created a conflict of interest for Clinton.

“Hillary Clinton and her staff don’t even bother about the information security. It was just a matter of time to gain access to the Clinton Foundation server,” he wrote.

Guccifer is widely believed to be one or more Russian hackers operating at the direction of, or at least in consultation with, the Russian government intelligence services. However, their specific identities remain unknown.

The release of the documents comes on the same day that WikiLeaks, the international whistleblower group led by Australian Julian Assange, had scheduled a press conference promising major revelations about Clinton.

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The press conference, held in the middle of the night in US time, was something of a bait-and-switch. Reporters and others who logged in were treated to what some described as a “commercial” for the organization, which is celebrating its 10th anniversary. There was no release of information about Clinton or her campaign.

Guccifer 2.0 nevertheless offered a shout-out to Assange, writing, “P.S. I’m pleased to congratulate WikiLeaks on their 10th anniversary!!! Julian, you are really cool! Stay safe and sound!”

In his post, Guccifer 2.0 claimed that the cache of files “contains docs and donors lists of the Democratic committees, PACs, etc.”

At first glance, the release contains a few elements that call the authenticity of the documents into question. For example, a listing of folders in the system contains one labeled “Pay to Play” -- a term that Clinton’s opponent, Republican nominee Donald Trump, frequently uses to characterize Clinton’s relationship with the foundation’s donors -- and one that a major foundation would be extremely unlikely to use even in internal communications.

Additionally, it contains a spreadsheet supposedly detailing the contributions to Democratic politicians from major banks, alongside the amount of money each was supposed to have received from the Troubled Asset Relief Program (TARP), which was implemented to help the financial services industry recover from the Great Recession. Guccifer 2.0 suggests that it is a list of, effectively, kickbacks. Again, it seems highly unlikely that a spreadsheet like that would be created by a political party, and there is no clear reason why it would be on the Clinton Foundation’s website in the first place.

This article was updated at 5:46 p.m. on Tuesday, Oct. 4.