Prompt Injection: A Hidden Threat in LLM Security
Prompt injection ranks No. 1 with OWASP and No. 12 in the incident record. The attack itself is invisible to a scan. | VentureBeat
Orchestration, Infrastructure, Data, Security
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Louis Columbus
10:24 am, PT, August 25, 2026
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A CISO who sees a low CVE count and deprioritizes prompt injection is reading the scoreboard wrong. Prompt injection has held the No. 1 spot on the OWASP Top 10 for LLM Applications for three consecutive years. When two leaders of that list checked it against 6,639 labeled real-world incidents, it came back at No. 12. The drop measures visibility rather than danger, because the attack operates where a vulnerability scanner cannot see it.
That finding belongs to Kyriakos “Rock” Lambros and Steve Wilson, two leaders of the OWASP Top 10 for LLM Applications project, who published it on arXiv on August 18 with the disclaimer attached. The analysis is exploratory, not peer reviewed, and not the official OWASP release, and the authors state it does not supersede the official list or its process.
The machinery behind it is real: 7,714 LLM security incidents from CVE, GitHub Security Advisories, OSV, and the AIAAIC AI-harm database, 6,639 of them labeled against a 20-entry taxonomy, and a Bayesian model that corrects each count for classifier error before setting the data-driven ranking beside the expert vote.
The comparison found no statistically detectable agreement between expert judgment and the public incident record. Cohen’s kappa comes in at 0.20 with a 90% interval running from negative 0.16 to 0.57. "The interval crosses zero, so we cannot rule out that the two rankings agree only by chance," they write. "The honest bottom line: weak agreement, not confirmation."
Lambros, co-lead of the OWASP GenAI Security Project Top 10 for LLM Applications and director of AI standards and governance at Zenity, put the finding in evidentiary terms in written answers to VentureBeat. "We had two ways of measuring the same risk, expert judgment and the public incident record, and they disagree with each other. Neither one is the truth,” Lambros said. "Two witnesses are contradicting each other, and we can’t tell you which one is lying."
The Attack Chain a Scanner Never Logs
The gap is structural. Prompt injection hides instructions inside the content a model reads, anything from a log entry to a support ticket to a document pulled back by retrieval. The agent then makes the tool call the attacker wanted, using credentials it legitimately holds. Nothing in that chain is a product defect, so the attack leaves no CVE behind for a scanner to find.
Defenses and Controls
The defenses that catch it are adversarial tests against the deployed system and hard caps on what the agent can reach, so a fooled model cannot touch anything expensive. The same logic argues for funding agent memory and MCP tool boundaries now, on architecture, rather than waiting for advisory volume that will always arrive a cycle late.
Wilson, Chief AI and Product Officer at Exabeam and project co-lead for the OWASP Top 10 for LLM Applications, named the control he would deploy first against exactly that chain:
"The first thing I’d do is put an authorization gate outside the model: the agent can propose the exact DNS change, but it cannot grant itself the authority to make it. Security rules written inside prompts may shape the model’s behavior, but they are still suggestions to the model, not enforceable security controls."
