How Twitter Helped Avert a Critical Exploit

A Twitter user helped prevent a 200 billion BitBTC exploit

article-image

Source: DALL·E

share

key takeaways

  • This vulnerability was not in Optimism’s code, but rather in a custom bridge provided by BitBTC
  • BitBTC’s custom bridge code did not acknowledge the specific layer-2 token being minted to the layer-1 address

A Twitter user has helped avert a potential exploit after publicly flagging a vulnerability in BitBTC’s Optimism bridge — the latest such near-miss amidst a year full of “successful” thefts. 

Lee Bousfield, a tech lead at Ethereum scaling solution Arbitrum — PlasmaPower0 on Twitter — published what he dubbed a critical exploit after he said his messages were ignored by BitBTC. 

Loading Tweet..

The BitBTC bridge to or from Optimism’s blockchain facilitates withdrawals of any token between layer-2 and a corresponding layer-1 wallet. But, the BitBTC code involved does not acknowledge what the layer-2 token actually is —and mints an arbitrary layer-1 to match. 

“That means an attacker could deploy their own token on Optimism, give themselves all the supply, and set that token’s L1Token to the real BitBTC L1 address,” Bousfield tweeted.

“When the attacker withdraws their malicious token through the BitBTC bridge, it gives them real BitBTC tokens on L1,” he said.

Of note, the apparent vulnerability was not in Optimism’s code, but rather in a custom bridge facilitated by BitBTC, according to Kelvin Fichter, an Optimism developer. Meaning, he said, no assets other than BitBTC assets were at risk.

“We put a lot of time and energy into the standard bridge and I highly recommend using the standard bridge rather than rolling your own custom bridge unless you really know what you’re doing,” Fichter tweeted.

The next day, an attacker — who claimed he was testing the code, tried to withdraw 200 billion BitBTC from Optimism. 

The exploit was able to be stopped as the process of withdrawing the token from the bridge would have taken seven days, and BitBTC in the interim patched the vulnerability via a software update.

“The attacks will now fail when they arrive on L1. Thanks everyone for making noise and helping get this fixed,” Bousfield tweeted.

Bousfield did not immediately return a request for comment.


Get the news in your inbox. Explore Blockworks newsletters:

Tags

Upcoming Events

Old Billingsgate

Mon - Wed, October 13 - 15, 2025

Blockworks’ Digital Asset Summit (DAS) will feature conversations between the builders, allocators, and legislators who will shape the trajectory of the digital asset ecosystem in the US and abroad.

recent research

Research

article-image

The company will pay a $0.05 dividend and a $0.35 ETH loyalty payout in ether

article-image

While the headline growth in the USDe supply is impressive, there’s often more than meets the eye

article-image

Purity tests are the only things keeping crypto “crypto”

article-image

Every transformational technology begins with utopian hopes, and then runs into the world as it is

article-image

US indexes were muted Monday as investors wait to hear from Chair Powell and President Trump

article-image

There’s easily enough cash for at least another 2-3 years of Otherside game development, according to Greg Solano