Experts challenge Yahoo’s assertion that state-sponsored hackers were behind a 2014 breach that resulted in 500 million lost records.

Twitter has forced a password reset on an unnamed number of accounts exposed this week in a dump of 32.8 million account names and credentials. A Russian hacker known as Tessa88 has been involved in a number of recent password disclosures with Twitter being the most recent. He shared the cache of Twitter data with...