Findings/agentic-browsers-act-on-hidden-content

Agentic browsers act on page content that users cannot see.

Reportedmeasured3 evidence records from 1 independent sourceassistant-drafted

Scope: what this does not show

Demonstrations by one research team (Brave, itself a browser maker) across three other browsers; vendors' fixes vary, and one of the cases used visible rather than hidden text.

Reported: Stated by one source and not yet corroborated or challenged.

Evidence

Aug 20, 2025

Brave discloses indirect prompt injection in Perplexity Comet agentic browser

Brave

Comet acted on instructions hidden in page content (for example white text or a spoiler tag).

Oct 21, 2025

Brave finds screenshot and navigation prompt injections in Comet and Fellou browsers

Brave

Comet read faint text hidden in screenshots; in Fellou the injected page text was visible, but was sent to the model on simple navigation.

Oct 31, 2025

Brave discloses hidden-HTML prompt injection in Opera Neon, fixed within a week of re-engagement

Brave

Opera Neon's assistant followed instructions in an invisible (opacity 0) page element.

Status history

2025-08-20ReportedBrave shows Comet treating page content as instructions. · record

What would change this: Independent replication across browsers, or a browser that separates visible from hidden content.
Evidence kind: measured: An experiment or evaluation produced the number.
Freshness: Evidence 330d old · recheck in 35 daysNewest evidence Oct 31, 2025. Half-life 365 days.
Methods tested: Indirect prompt injection
Topics: Prompt injection
Attack surface: Untrusted content

Cite this record

Fide AI. "Agentic browsers act on page content that users cannot see.." Agentic Cyber Explorer, record agentic-browsers-act-on-hidden-content. https://agentic-cyber-explorer.pages.dev/findings/agentic-browsers-act-on-hidden-content/ (corpus as of 2026-09-26).

BibTeX

@misc{fide-ace-agentic-browsers-act-on-hidden-content,
  author = {{Fide AI}},
  title = {Agentic browsers act on page content that users cannot see.},
  howpublished = {Agentic Cyber Explorer},
  year = {2026},
  url = {https://agentic-cyber-explorer.pages.dev/findings/agentic-browsers-act-on-hidden-content/},
  note = {Record agentic-browsers-act-on-hidden-content; corpus as of 2026-09-26}
}

Data: JSON · CC BY 4.0

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