The hacks on Silicon Valley’s biggest names continue, this time with Twitter CEO Jack Dorsey having both his Twitter and Vine accounts apparently breached.

Hacking group OurMine Security claimed responsibility. The group is also behind recent high-profile hacks on the social media accounts of Facebook founder Mark Zuckerberg and Google’s Sundar Pichai.

The hackers posted a message saying, “Testing your security,” the same message posted in other attacks.

The hack appears to have come through Vine, which Twitter owns, according to The Guardian newspaper.

Twitter told the paper that it does not “comment on individual accounts for privacy and security reasons.”

Last month, Twitter locked down some accounts after a leak of username and password information. (VOA)

•Photo shows Twitter CEO Jack Dorsey.