WASHINGTON—A hacker posted cellphone numbers and other personal information of nearly 200 current and former congressional Democrats on Friday, the latest public disclosure of sensitive records this election season.

The hacker, or group of hackers, going by the name “Guccifer 2.0” said the records were stolen as part of a breach of the Democratic Congressional Campaign Committee. A number of files were posted onto Guccifer 2.0’s website, including a spreadsheet that has information, such as phone numbers and email addresses,...