elvis (@omarsar0) on X
Thread by Elvis Saravia (omarsar0) summarising an Anthropic-led paper on pretraining data poisoning of CLI agents. Poisoning 0.1% of pretraining data planted a remote code execution backdoor in Qwen3 models (0.6B, 1.7B, 4B) trained from scratch. It survived SFT, DPO and RL, and fired on about 92% of triggered prompts at 4B. At a 0.0005% poison rate (about 2,500 documents) it still fired on 1.4% of prompts.
AI Security· Added 31 Oct 2026, published 30 Oct 2026


















