Whole Foods near Axios World HQ in Arlington, Va., on Day 2 of Amazon control

Researchers at Zhejiang University were able to hack voice assistants like Alexa and Siri using frequencies too high for humans to hear that were still picked up by the devices.

Why it's scary: Many "hey Siri" functions may be harmless, but the researchers could also tell an Amazon Echo to "unlock the back door," redirect the navigation system of an Audi Q3, or install malware on an iPhone. The researchers used a smartphone with just $3 worth of extra hardware. With a little technological expertise, this method could easily be replicated.

Why it matters: Security experts worry the the so-called Internet of Things (including connected devices like digital assistants) are highly vulnerable to security breaches and other attacks not anticipated by manufacturers.

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Biden releases 2019 tax returns ahead of debate

Photo: Alex Wong/Getty Images

Joe Biden's campaign released his 2019 tax returns on Tuesday, showing that he and his wife, Jill, paid nearly $300,000 in federal taxes last year.

Why it matters: The release, timed just hours before the first presidential debate, comes days after a bombshell New York Times report said that President Trump paid only $750 in federal taxes in 2016 and 2017. Biden's team is hoping to make the tax contrast a sticking point during their showdown.

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Coronavirus dashboard

Illustration: Sarah Grillo/Axios

  1. Global: Total confirmed cases as of 1 p.m. ET: 33,443,701 — Total deaths: 1,003,337 — Total recoveries: 23,200,183Map.
  2. U.S.: Total confirmed cases as of 1 p.m. ET: 7,159,222 — Total deaths: 205,345 — Total recoveries: 2,794,608 — Total tests: 102,342,416Map.
  3. Health: Americans won't take Trump's word on the vaccine, Axios-Ipsos poll finds.
  4. States: NYC's coronavirus positivity rate spikes to highest since June.
  5. Sports: Tennessee Titans close facility amid NFL's first coronavirus outbreak.
  6. World: U.K. beats previous record for new coronavirus cases.

NYC's coronavirus positivity rate spikes to highest since June

New York Mayor Bill de Blasio. Photo: Noam Galai/Getty Images

New York City's coronavirus positivity rate has ticked up to 3.25%, its highest since June, Mayor Bill de Blasio said at a news conference on Tuesday.

Why it matters: The jump — from 1.93% on Monday — came on the first day that public elementary classrooms reopened in the city after months of closures, but guidelines state that all public schools will have to shut if the citywide seven-day positivity rate stays above 3%.