The security firm Trusted Sec said the latest data leak -- first reported by Vice Media's website Motherboard -- "does appear to be legitimate like the other dump."
The new data leak comes two days after the release of some 32 million emails and user account information.
The new release "appears to contain all of (parent company chief executive Noel Biderman's) business/corporate emails, source code for all of their websites, mobile applications, and more," TrustedSec said in a blog post.
Motherboard reported that the data file posted on the "dark Web," which is not easily accessible, was some 20 gigabytes, or twice as large as the file released on Tuesday.
Ashley Madison is known for its slogan: "Life is short. Have an affair." It helps connect people seeking to have extramarital relationships and is owned by Toronto-based Avid Life Media (ALM).
The file contained a message that appeared to be directed at ALM's Biderman, who at one point cast doubt on the credibility of the first data leak.
"Hey Noel, you can admit it's real now," the message said.
TrustedSec said the release of the source code poses grave security risks.
"Having full source code to these websites means that other hacker groups now have the ability to find new flaws in Avid Life's websites, and further compromise them more," the blog said.
"If there was any question to the validity of the data before -– those should be removed now."
- 'Biggest hypocrite ever' -
The data leak already appeared to lead to embarrassing and potentially calamitous consequences.
A number of maps and searchable databases have appeared online which could identify users.
US television personality Josh Duggar, known as a family values activist, acknowledged he had used Ashley Madison after being outed by the news website Gawker.
"I have been the biggest hypocrite ever. While espousing faith and family values, I have been unfaithful to my wife," said a statement from Duggar, a former head of the Family Research Council lobby group.
"I humbly ask for your forgiveness. Please pray for my precious wife Anna and our family during this time."
US Defense Secretary Ashton Carter said the Pentagon was looking into whether members of the US military were on the site, since adultery may be prosecuted in the armed forces.
"I'm aware of it -- of course it's an issue because conduct is very important," Carter said in response to a question at a Pentagon briefing.
"And we expect good conduct on the part of our people. And to the last part, yes. The services are looking into it and as well they should be."
The release of files by the hackers came a month after the data was stolen by hackers identified as the "Impact Team," who said they were trying to shut down the site for cheaters.
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