Six out of nine of the most popular AI chatbots routinely exposed user input to third parties, new European research reveals.

Multiple chatbots disclosed sensitive user data to advertising companies through trackers – a piece of code used to identify and target users on the web with customised advertisements, which are widely used across the web.

And tech companies may have been able to link conversation summaries with personal identifiers, allowing users to be targeted based on their conversations with AI.

The researchers aimed to establish the connection between existing tracking technologies and AI advertising. “We basically connected the dots, and wanted to test whether and how AI bots integrate tracking and advertising services,” said Narseo Vallina-Rodriguez, who led the study.

Vallina-Rodriguez is part of a group of researchers who investigated the use of ad trackers in the most popular AI providers with colleagues at Imdea Networks, a public research institute in Madrid.

Their findings warn of “tensions” between tech company practices and obligations to users under privacy laws.

Sensitive user-data shared 

“We already knew that tracking is pervasive, even without AI. But now you have the most super-invasive phenomena on the internet, which is AI,” said Itxaso Domínguez de Olazábal, a policy adviser at digital rights group Edri.

Users often share information about their health, psychological state, finances, and other intimate matters in AI prompts. The study shows how users who asked AI questions about such matters could have sensitive details summarised in a chat title shared with third parties. 

“Now, big tech has access to much more intimate information which users tell AI. It’s crazy, the details are so intimate. My friends ask AI bots about relationships, or they use ‘doctor AI’,” said Domínguez de Olazábal.

GDPR rules require companies to make clear how users’ data is harvested, but researchers question “ambiguous expressions” used to explain the role of trackers in T&Cs.

And the ePrivacy directive requires users to consent to cookies unless they are “strictly necessary”, but researchers found that even when users rejected non-essential cookies, AI bots Perplexity, DeepSeek, Gemini, Copilot, ChatGPT and Claude still connected to Google Ads.

All of the top nine most popular chatbots were found to integrate at least one third-party advertising or tracking service.

Consent and transparency ‘shortcomings’

A preview of the study, released in May, prompted the Spanish privacy watchdog AEPD to request for the European Data Protection Committee (EPDC) to share preliminary findings with European counterparts “for knowledge and assessment”.

The final paper, titled ‘Prompt like a Butterfly, Sting like a Tracker’, has been accepted for publication at an academic forum in Delft next year.

Findings “highlight tensions between current practices and obligations under the GDPR and ePrivacy Directive, exposing broader shortcomings in consent, access control, and transparency mechanisms,” the paper reads.

It reveals that Grok, operated by Elon Musk’s SpaceXAI, exposed public links to conversations by default, allowing trackers to routinely access whole conversations, with TikTok also processing screenshots of Grok conversations.

Meanwhile, Mistral, France’s flagship AI firm, did not offer users a choice to reject non-essential cookies. 

But offering such a choice might soon be redundant anyway. “The tracking industry is moving towards paradigms called cookie-less and identity-based tracking. So they are circumventing anti-tracking capabilities,” Vallina-Rodriguez told EUobserver.

One way, or another …

Some suggest that using browsers with anti-tracker technologies can help users avoid surveillance.

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As AI-powered biometric identification is adopted by police, national authorities should go beyond legal requirements to build trust within the public, a watchdog report has advised.

“To build public trust, law enforcement should publish the results of their fundamental rights impact assessments, going beyond what the AI Act requires,” said the Fundamental Rights Agency (FRA), an EU branch which keeps tabs on citizens’ freedoms, in Vienna on Wednesday (30 September).

After collecting data from seven EU countries (France, Germany, Greece, Hungary, Italy, the Netherlands, and Ireland), the watchdog warned that several member states have yet to put necessary frameworks in place as they adopt automated systems to identify people.

Remote biometric identification is increasingly used to compare people’s profiles against databases or watch lists, but as the technology develops it could be rolled out for real-time use in public areas. 

“With clear safeguards and independent oversight, remote biometric technologies can support policing without undermining the very freedoms it is meant to safeguard. Ultimately, it is about trust,” said FRA chief Sirpa Rautio.

Call for disclosure mechanisms 

Effective implementation of the EU AI Act requires clear national laws and consistent safeguards to ensure that AI-powered technologies are not used to identify people taking part in peaceful demonstrations or public gatherings, the FRA says.

The body warns that automated identification of live data may affect people’s private lives and interfere with their right to protection of personal data.

In its survey, 37 percent of people said they fear their data could be used for unauthorised purposes. 

And 29 percent of people surveyed by FRA said they would be less willing to take part in peaceful demonstrations or protests if facial recognition was used.

The FRA is worried that surveillance tech powered by AI could be used in exactly those scenarios.

In principle, the EU’s AI Act adopted in 2024 bans real-time remote biometric identification systems in public spaces. But exemptions exist for law enforcement authorities using the technology for finding victims or missing persons, to prevent threats to life or physical safety, stop a terror attack, or to find criminal suspects.

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The European Commission is being pressed to deliver an animal cage ban by 2027 after failing to meet previous commitments.

Several hundred animal rights activists gathered at the EU’s office for health and food safety in Brussels on Monday (28 September) to encourage a ban on poultry cages and on the killing of male chicks. 

The commission’s livestock strategy had committed in July to proposing legislation to outlaw the two practices by the end of 2026, with similar legislation on pig welfare expected to follow by mid-2027.

The legislation stems from a European Citizens’ Initiative (ECI) signed by 1.4 million people in 2021 to ‘End the Cage Age’. A vast majority of MEPs also subsequently voted to endorse the transition to improved animal welfare. 

And while the commission had originally promised to table a proposal by 2024, this was derailed by farming lobbies and the deadline elapsed.

“We are here [at Monday’s protest in Brussels] because the EU has been delaying meaningful reforms for animals for years,” said Ombretta Alessandrini from Animal Equality, which organised the rally.

“Our democratic ask needs to be respected. We feel betrayed by the EU’s broken promises and we want the commission to do what they say,” she told EUobserver.

Animal Equality has also joined legal action against the commission over its broken promises, in a case examined at the European Court of Justice in March.

The commission is legally obliged to respond to a citizens’ initiative once it reaches 1m or more signatures. 

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