Researchers introduced market signal injection (MSI), a new type of attack that manipulates large language model (LLM) pricing agents by manipulating market data presentation without changing numerical values. The study evaluated nine open-weight models and three proprietary models in simulated markets, finding that sentiment-based attacks caused significant behavioral shifts, affecting profits and consumer surplus. The study suggests that LLM pricing agents are vulnerable to data presentation attacks and recommends defenses that account for agent interactions.