More than 600 gigabytes of files left unsecured on an Amazon server by third-party communications company BroadSoft were leaked last month.
The four million Time Warner Cable records contain the personal details of its customers, and include usernames, email addresses and financial transaction information, according to Gizmodo.
"Certain non-financial information of legacy Time Warner Cable customers who used the MyTWC app became potentially visible by external sources," Time Warner Cable parent Charter Communications said in a statement to CNBC.
Charter clarified that once the unlocked server was discovered, Broadsoft immediately removed the information and began a joint investigation into the incident. More sensitive customer information, such as credit card information or Social Security numbers, was not apparently compromised in the leak, the Gizmodo report said.
"There is no indication that any Charter systems were impacted," Charter said.
Shares of Charter declined less than half a percent in midday trading Friday, to $396.83 per share.
Read more from Gizmodo here.
Correction: This story has been revised to reflect that the records were those of some Time Warner Cable customers.