Grant de Swardt, an independent AI consultant in East Sussex, said unauthorized activity drained tokens from his Claude Max 20x account despite no use, and Anthropic later tied it to a compromised session key.. De Swardt said token usage rose on Aug. 4 while he was not working, then climbed again the next day after he disabled attachments and stopped using the service..
“In the clearest controlled interval, it increased from 45% to 55% while I performed no work, scheduled Cowork tasks were paused or completed, Dispatch/cloud execution was disabled, and there was no corresponding active local Claude Code task,” de Swardt told TechCrunch.. After he contacted Anthropic and asked for an itemized usage list, the company did not provide one but suspended his paid account, invalidated all sessions and server-side Claude Code tokens, and refunded him 44.49 pounds for the unused portion of his $200-a-month subscription..
De Swardt told TechCrunch the suspension disrupted his business because he uses AI agents for client work and internal operations, including loading purchase-order data from emails into accounting software, handling administrative work, website design and coding.. Anthropic later told him a compromised Claude session key had been used to mint unauthorized Claude Code OAuth tokens.
De Swardt said the company told him the account “appeared to have been used by an unauthorized-looking third-party service to handle activity for other people, but they could not determine how it obtained access.”. After posting about the incident on Reddit, de Swardt said he found similar complaints from other users.
One user wrote that an account was auto-upgraded without consent, a card was charged, and usage rose from 0% to 100% without any activity.. Another user said usage jumped from 0% to 49% in 12 minutes after only a few prompts and a web search. A GitHub report from another Claude user said their account exhausted its maximum tokens each day for three days despite no use, with other users posting similar experiences in the thread..
Two users posted emails from Anthropic saying their tokens were being stolen by a bad actor using infostealer malware. “We have recently become aware of a bad actor that is using common infostealer malware to steal Claude login sessions from people’s computers, then using those login sessions to access Claude accounts and consume their usage,” the email said..
Anthropic told those users it had signed them out, invalidated existing authorizations, issued some refunds and warned them that they might have malware. The company also said the malware was not caused by using Claude and could be picked up online through infected software or malicious ads..
De Swardt said he did not receive that warning email and found no evidence that his computer had been compromised. He said he still could not determine how access was obtained.. His account was reinstated after about two weeks, but he canceled his subscription and switched to Cursor, citing slower support and the lack of itemized token data.
When asked how users can identify misuse of their accounts, Anthropic declined to comment.. Featured image credit. Tags: Anthropicclaude
