Twitter (NYSE:TWTR) was the victim of an extensive hack late Wednesday afternoon. Numerous high-profile users of the messaging platform, including Tesla CEO Elon Musk, ex-Microsoft leader Bill Gates, and former U.S. Vice President Joe Biden, saw their feeds hijacked.

In them, a post appeared that evening promising double returns on $1,000 donations made online, in Bitcoin within a 30-minute time window. Readers were directed to an outside URL for the donations.

Hacker using two smartphones and a laptop.

Image source: Getty Images.

It is unknown what person or persons hacked the platform, and it's unclear at the moment how much the apparent scammers reaped in donations. The Bitcoin posts were deleted, and Twitter froze an unspecified number of accounts while it worked on a fix. The company says that access to most of the frozen accounts has been restored.

"We detected what we believe to be a coordinated social engineering attack by people who successfully targeted some of our employees with access to internal systems and tools," said a post on the official Twitter Support account Wednesday night. "We know they used this access to take control of many highly visible (including verified) accounts and Tweet on their behalf."

Twitter is continuing to update the public on the situation via the Twitter Support account.

The hack is particularly alarming in the run-up to the national elections in November. Concerns have already been raised about the security of U.S. voting systems. This incident likely will heighten such worries.

Politicians have already begun taking action on the Twitter incident. In a letter sent Thursday to Twitter CEO Jack Dorsey, Republican Senator Roger Wicker of Mississippi has requested that the tech company brief the Senate's Commerce Committee on the incident by next Friday.

Not surprisingly, investors traded Twitter's shares down on Thursday. Shares fell by just over 1% on Thursday, a steeper drop than that suffered by the broader stock market.