Gartner urges brands to block agentic AI browsers 'now'

UK brand owners have been warned that agentic browsers are far too risky for most to use, and should be blocked immediately and for the foreseeable future or risk exposing sensitive user data, such as active web content, browsing history, and open tabs.

That is the stark conclusion of a new advisory document from Gartner, “Cybersecurity Must Block AI Browsers for Now,” in which research VP Dennis Xu, senior director analyst Evgeny Mirolyubov, and VP analyst John Watts observe that “default AI browser settings prioritise user experience over security.”

The analysts’ definition of an AI browser encompasses tools like Perplexity’s Comet and OpenAI’s ChatGPT Atlas that include an “AI sidebar” that offers users the chance to summarise, search, translate, and interact with web content using AI services provided by the browser’s developer and an agentic transaction capability that allows the browser to autonomously navigate, interact with, and complete tasks on websites, especially within authenticated web sessions.

Gartner’s document warns that AI sidebars mean “sensitive data – such as active web content, browsing history, and open tabs – is often sent to the cloud-based AI back end, increasing the risk of data exposure unless security and privacy settings are deliberately hardened and centrally managed”.

The consultancy firm suggests it is possible to mitigate those risks by assessing the back-end AI services that power an AI browser to understand if their security measures present an acceptable risk to your organisation.

If that process leads to approval for use of a browser’s back-end AI, Gartner advises organizations should still “Educate users that anything they are viewing could potentially be sent to the AI service back end to ensure they do not have highly sensitive data active on the browser tab while using the AI browser’s sidebar to summarize or perform other autonomous actions.”

The authors also suggest that employees “might be tempted to use AI browsers and automate certain tasks that are mandatory, repetitive, and less interesting” and imagine some instructing an AI browser to complete their mandatory cybersecurity training sessions.

The warning follows a McKinsey report which shows that on the one hand, 50% of CMOs rank gen AI-enabled marketing as a top three fastest growing investment area; on the other, GenAI and agentic AI rank towards the bottom of their 2026 priority list – 17th out of 20 marketing priorities.

McKinsey reckons this disconnect could mean AI initiatives will not scale towards maturity and bottom-line impact but instead remain stuck in pilots.

McKinsey senior partner Jesko Perrey commented: “GenAI is the tip of the spear for marketing. To make inroads organisations need to match their increased GenAI spend with clear attention and attribution. If these don’t come together, CMOs are in danger of a marketing own-goal.

“The true winners will be those who strike the right balance between building their GenAI marketing muscle and rekindling the fundamentals of branding and marketing.”