Prompt injection live bug bounty (Anthropic with Gray Swan)
Expert red teamers submit prompt injection attacks against hidden frontier models in tool use, coding and computer use scenarios. Score is attack success rate.
Each round runs for about a week with new scenarios. Claude models are tested without product prompt injection protections.
- Made by
- Anthropic (with Gray Swan)
- Released
- May 2026
- Kind
- Jailbreaks and prompt injection
- Level
- Expert
- Scored
- Checked automatically
- Answers
- Agent task
- Tasks
- Kept private
- Strongest model tested
- Claude Opus 5 #10 on the capability index
- Last in a system card
- July 2026
- Last model added
- July 2026
Claude Opus 5 leads with 0.08% among models released by July 2026
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
The newest model with a score here came out in July 2026, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- Claude Fable 5.2
-
Gemini 4 Carbon - GPT-6 Astra
- Claude Opus 5.5
- and 15 more
- 1 Claude Opus 5 0.08%
- 2 Claude Sonnet 5 0.19%
- 3 Claude Opus 4.8 0.40%
Source: Labs’ model cards
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Opus 5 | 0.08% | Jul 2026 | Lab model card | |
| 2 | Claude Sonnet 5 | 0.19% | Jun 2026 | Lab model card | |
| 3 | Claude Opus 4.8 | 0.40% | May 2026 | Lab model card |
3 models have held number one in labs’ own numbers since its release in May 2026
Lab claims count from the day the card came out, independent runs from the model’s release.
Source: Labs’ model cards
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Source: Labs’ model cards
Labs report it only in system cards
We read the headline results of 522 launch posts from 52 labs, and none of them list this benchmark. Some system cards do, below.
3 system cards report it, from 1 lab
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| Jul 24, 2026 | Claude Opus 5 system card | 0.08 | Live bug bounty with Gray Swan, attack success rate over all valid attempts, 11 scenarios, high effort, no product protections, lower is better. Tool use 0.13%, coding 0.04%, computer use 0.00%. Added in the August 19 update (5.2.2.1, Figures 5.2.2.1.A and B) | Robustness |
| Jun 30, 2026 | Claude Sonnet 5 system card | 0.19 | Live bug bounty with Gray Swan, share of unique attacks succeeding over 11 scenarios, high thinking effort, no product protections, lower is better (tool use 0.35%, coding 0.1%, computer use 0.07%) (5.2.2.1, Figures 5.2.2.1.A and B) | Robustness |
| May 28, 2026 | Claude Opus 4.8 system card | 0.4 | One-week live bug bounty with Gray Swan, 12 scenarios across tool use, coding and browser use, attack success rate over 15,249 submitted attempts, high thinking effort, no product protections, final results per the June 17 correction, printed on chart, lower is better (5.2.2.1, Figure 5.2.2.1.A) | Robustness |
More in Safety and alignment
- FORTRESS In use Paired adversarial and benign national-security misuse prompts. Rubric-graded risk score on adversarial and over-refusal score on benign prompts. Claude Opus 5.5 5.78%
- StrongREJECT In use Forbidden-prompt jailbreak benchmark with a rubric grader that scores how useful a non-refusal actually is.
Inkling 98.6% - Gray Swan IPI Arena benchmark In use Indirect prompt-injection attacks from public red-teaming competitions replayed on tool, coding and browser agents. Attack success rate at k attempts. Gemini 4 Carbon 0%
- DistressBench In use Models reply as a chatbot to 718 simulated users in psychological crisis, in single-turn and multi-turn chats. Three judge models score replies against clinician-written rubrics.
Muse Spark 1.2 88.4% - Lakera B3 (Backbone Breaker Benchmark) In use Crowdsourced prompt-injection attacks hit backbone LLMs inside agent threat snapshots at three defense levels. The score is attack resistance, 100 minus the board's vulnerability percentage. Claude Opus 4.5 89%
- IHEval In use Models face conflicts between system, user and tool instructions. Reports a composite score for following the higher-priority instruction. GPT-4o 70%