# New serious vulnerabilities spiked around release of Claude Mythos Preview > Source: > Published: 2026-07-03 21:16:16+00:00 Epoch's work is free to use, distribute, and reproduce provided the source and authors are credited under the Creative Commons BY license. ## Learn more about this graph In April 2026, Anthropic [announced](https://red.anthropic.com/2026/mythos-preview/) that its latest internal model (Claude Mythos Preview) was capable of autonomous cybersecurity vulnerability discovery and exploitation. Since then, both [Anthropic](https://www.anthropic.com/glasswing) and [OpenAI](https://openai.com/daybreak/) have launched efforts to use frontier models to harden critical software before malicious actors are able to use the same models for harm. We show that the number of Common Vulnerabilities and Exposures (CVEs) jumped significantly following these announcements. Compared to the previous monthly record before the Mythos Preview announcement, the number of high- and critical-severity vulnerabilities increased more than 3.5x in June.