Twitter CEO Jack Dorsey’s own Twitter account was briefly hijacked early this morning, topping off a recent string of similar attacks. The hack appears to have been the work of OurMine, the same group that previously compromised social media accounts belonging to Facebook CEO Mark Zuckerberg, former Twitter CEO Dick Costolo, and Google CEO Sundar Pichai.
Early Saturday morning, the hackers posted a string of clips on Twitter’s own Vine video service mocking the company. At least one included a skewering theme song and a message: “Hey, its OurMine,we are testing your security” [sic]. The tweets were reportedly scrubbed by 3:25 a.m. Eastern, but tech website Engadget grabbed screenshots.
Get Data Sheet, Fortune’s technology newsletter.
In the Costolo and Zuckerberg hacks, OurMine accessed Twitter accounts through connected third-party applications or through old or recycled passwords. Tech website Android Authority reports that all of last night’s compromised tweets from Dorsey came via Vine, so the same tactic seems to have been used here.
The detail is significant because Twitter has stated that the recent hacks were the result of a variety of leaks from third-party sites—not from any compromise of Twitter’s own servers.
For more on Twitter, watch:
The motivation for compromising Dorsey’s account remains opaque. (Most hackings of this nature are meant only as vandalism, intended to cause a stir.) As business website Quartz outlined, OurMine seems to be comprised of neither legitimate “white hat” security activists nor political hacktivists along the lines of Anonymous, the well-known collective. Though OurMine has laid claim to large thefts, the group’s main goal seems to be harassment.
Dorsey and Twitter have not yet commented on the incident.
