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Opus 5 may have solved browser-based prompt injection, the biggest security flaw haunting AI agents

Technology · en

Opus 5 may have solved browser-based prompt injection, the biggest security flaw haunting AI agents

The Decoder · Jul 25, 2026, 10:43 AM UTC

Opus 5 combined with Auto Mode hits a zero percent prompt injection success rate for browser agents across 129 test scenarios. Without those extra protection layers, the rate is 3.7 percent. If these numbers hold up in practice, Anthropic may have cracked one of the biggest security problems facing AI agents that operate in browsers.…