https://www.jiri123.xyz/ Field notes from a security researcher working in the age of AI. en-US https://www.jiri123.xyz/posts/llm-prompt-caching/ https://www.jiri123.xyz/posts/llm-prompt-caching/ Thu, 08 Oct 2026 00:00:00 GMT Notes AI APIs charge as little as a tenth, sometimes a fortieth, of the normal input price for tokens they have seen before. The discount comes from skipping work the GPU already did. Most providers cache automatically, and keeping what changes at the end of the prompt gets you more hits. A cache hit only means your own organization sent the same prefix, although a 2025 audit found seven providers where caches were shared across users. https://www.jiri123.xyz/posts/jev-for-bug-bounties/ https://www.jiri123.xyz/posts/jev-for-bug-bounties/ Sun, 04 Oct 2026 00:00:00 GMT Notes TypeSafe's Jev answers typed questions in well under a second for a fraction of a cent. I ran it on the code of a real Cantina contest, where two models together put 5 of the 9 confirmed bugs in their top 15 functions. That makes it a decent way to pick what to read first. It missed every bug that needed a neighboring function and can't say why a function looks wrong, so I still wouldn't use it to find bugs. As a judge, I'd use it to sort duplicates. https://www.jiri123.xyz/posts/write-the-poc/ https://www.jiri123.xyz/posts/write-the-poc/ Sun, 04 Oct 2026 00:00:00 GMT Audits I was annoyed when Cantina made proofs of concept mandatory. After a year of competing and judging, and a flood of AI-generated reports, I think it's the most useful rule in audit competitions. https://www.jiri123.xyz/posts/ownable2step-oz5-initial-owner/ https://www.jiri123.xyz/posts/ownable2step-oz5-initial-owner/ Fri, 02 Oct 2026 00:00:00 GMT Notes In OpenZeppelin Contracts Upgradeable 4.x, calling __Ownable2Step_init() made the caller the owner. In 5.x it does nothing. Bump the dependency without updating your initializers, and new deployments end up with no owner at all. https://www.jiri123.xyz/posts/paymentprocessor-nft-rescue/ https://www.jiri123.xyz/posts/paymentprocessor-nft-rescue/ Wed, 30 Sep 2026 00:00:00 GMT Incidents In September 2026, an approval exploit drained NFTs and WETH from wallets that had approved Limit Break's Payment Processor. Here is what happened, why I stepped in as a whitehat, and how the assets went back to their owners.