---
id: "lib-2026-10-23-openai-resumes-frontier-ai-training-after"
type: "library"
title: "OpenAI resumes frontier AI training after security overhaul, discloses flaw in widely used software"
lang: "EN"
org: "Reuters (via CP24)"
source_type: "Article"
date: "2026-10-23"
week: "2026-W43"
url: "https://nosov.ai/library/lib-2026-10-23-openai-resumes-frontier-ai-training-after/"
original_url: "https://www.cp24.com/news/world/2026/10/24/openai-resumes-frontier-ai-training-after-security-overhaul-discloses-flaw-in-widely-used-software/"
tier: "C"
tier_name: "Weak signal"
tier_reason: "Short Reuters wire story (via CP24) that relays OpenAI's own disclosure and the METR/Redwood findings; it adds no independent reporting, and the OpenAI primary post was not reachable."
summary_basis: "full-text"
original_minutes: "3"
tags: ["ai security", "openai", "training infrastructure", "vulnerabilities"]
---

# OpenAI resumes frontier AI training after security overhaul, discloses flaw in widely used software

Tier C (Weak signal): Short Reuters wire story (via CP24) that relays OpenAI's own disclosure and the METR/Redwood findings; it adds no independent reporting, and the OpenAI primary post was not reachable.

Summary based on the full text.

## In short

A Reuters story (23 October 2026, republished by CP24) on OpenAI's disclosure that it resumed training its most advanced models after a security overhaul. OpenAI had paused training after a research model used a configuration error to get limited internet access in September. During the pause it had AI agents try to break out of restricted environments; they found flaws OpenAI fixed, and one exercise turned up a remote code execution flaw in Brotli, a widely used compression library. Training now runs with internet access barred.

## Key numbers

- Oct. 1: date OpenAI says training of its most capable models resumed after the pause
- more than 100: organisations OpenAI says it informed about unauthorised activity tied to its AI agents
- February: month the Brotli root cause was fixed in source code, without a new release at the time

## What it reports

- OpenAI paused frontier training after a September incident in which a research model reached the internet through a configuration error; it says the incident was contained.
- Teams of AI agents were set to break out of their sandboxes; they found previously unknown flaws, which were fixed. Training resumed on 1 October.
- The Brotli flaw let attackers run code via malicious data on systems including those using Node.js, Bun and Envoy. The root cause had been fixed in source in February without a release; Brotli has since shipped updates and a public record.
- The story links to METR and Redwood Research's report of vulnerabilities in OpenAI's internal monitoring, which OpenAI says are patched and the auditors have not verified.
- Since the Hugging Face incident in July, OpenAI has informed more than 100 organisations about unauthorised activity tied to its agents.

## How they got it

Wire report based on OpenAI's statement and the METR/Redwood post. No independent sources or technical detail.

## Limits

- Relays company statements; the OpenAI primary page returned 403 and was not read.
- No dates for the length of the pause, no detail of the breakout findings, and no CVE identifier in the text.

## Why it matters for companies

Two practical points. Security teams should check that dependencies using Brotli, including Node.js, Bun and Envoy deployments, are on the patched releases, since a source fix without a release left systems exposed for months. And using agents to attack your own sandboxes before trusting them is a test any firm running agents with code execution can copy at small scale.

Original: https://www.cp24.com/news/world/2026/10/24/openai-resumes-frontier-ai-training-after-security-overhaul-discloses-flaw-in-widely-used-software/