Matthew Hanley, 22, and Connor Allsopp, 20, admitted charges relating to the massive data breach in October 2015.
The Old Bailey heard Hanley hacked into the telecom giant's website and shared a customer's personal and financial details with Allsopp.
The pair, of Tamworth, Staffordshire, were told they would be sentenced in May.
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Hanley supplied data for hacking to another man and gave Allsopp the personal and financial details of a TalkTalk customer for the use in fraud.
Allsopp admitted supplying a customer's details for fraud and as well as files for hacking.
Hanley, of Devonshire Drive, denied other charges of hacking into Nasa, the National Climatic Data Centre and another 23 websites including Spotify, Telstra, the RAC and The Eton Collection which were ordered to lie on file.
Allsopp, of Coronation Street, pleaded guilty at an earlier hearing.
Judge Michael Topolski QC ordered reports for both defendants and adjourned sentencing until 31 May.
In November last year, a 17-year-old youth was handed a 12-month rehabilitation order after he admitted sparking off the TalkTalk hacking when he posted details of a chink in the firm's online security.
Even though he did not gain from it, the youth paved the way for others to exploit the weakness for money by accessing the data of 160,000 people.
The teenager found the vulnerability in the TalkTalk website using "legitimate software" and shared details of this online.
The TalkTalk website was targeted more than 14,000 times after the boy exposed the vulnerability.
The firm said the fallout from the cyber attack in October 2015 cost it Â£42m.
The teenager told magistrates at Norwich Youth Court he was "just showing off" to his "mates".
Two friends have admitted their part in a Â£42m hack attack on the TalkTalk website.