Simon Willison’s Weblog

Response Splitting Risk. Important reminder that you should always ensure strings used in HTTP headers don’t contain newlines.

Posted 19th October 2008 at 11:58 pm

Recent articles

Wilson Lin on FastRender: a browser built by thousands of parallel agents - 23rd January 2026
First impressions of Claude Cowork, Anthropic's general agent - 12th January 2026
My answers to the questions I posed about porting open source code with LLMs - 11th January 2026

http 100 rails 74 responsesplitting 1 security 573

Monthly briefing

Sponsor me for $10/month and get a curated email digest of the month's most important LLM developments.

Pay me to send you less!

Sponsor & subscribe