Bitcoin closed the third quarter up 40%, outrunning every major asset even as Treasury yields climbed to their highest in more than two decades. Investors poured billions of dollars into exchange-traded funds tied to BTC and other tokens, and several altcoins rallied even harder, leaving analysts convinced a new bull run has arrived.
Yet amid the rally, one familiar stain on the industry's image kept spreading. That’s hacks and exploits. The money lost in these incidents is small next to the billions flowing into ETFs, but the damage to crypto's reputation is harder to wave away.
Crypto suffered 247 security incidents in the third quarter, with losses totaling $1.26 billion, according to data tracked by crypto security firm CertiK . Losses for the year so far stand at $2.68 billion. September was the worst month yet, with 99 incidents, the most since February 2025, and $768.5 million stolen, the largest monthly haul of 2026.
For now, the losses barely register against the capital arriving through ETFs, Sondergaard explained, adding that most institutions are buying crypto through regulated, familiar wrappers and staying away from DeFi protocols altogether.
CertiK said the numbers show how deeply rooted the problem remains.
"September was a stark reminder of how quickly the threat landscape can shift. With both losses and incident count reaching their highest levels of 2026, the month's data reinforces the need for security across every layer," it said on X .
The insurance safety net remains relatively small and is shrinking relative to risks. CoinGecko's State of Crypto Security Report 2026 released at the end of August noted this trend, and put the on-chain crypto insurance coverage capacity at $130.2 million, down 20.2% from $163 million last year.
Overall the insurance sector has struggled to match risks, as CoinDesk noted early this year.
Amid all this, artificial intelligence (AI) is adding a fresh threat.
Security firm Blockaid expects multiple incidents involving AI agents, with prompt injection, where hidden instructions trick an AI agent into acting against its user, the most likely route.
To conclude, the bull market may be back, but so are the malicious entities trying to cash in on its weak spots.
Read more: For analysis of today's activity in altcoins and derivatives, see Crypto Markets Today . For a comprehensive list of events this week, see CoinDesk's Crypto Week Ahead .