Hackers hijacked 4,000 websites, including government ones, to mine crypto-currencies without visitors knowing. Scott Helme, the security researcher who found the flaw, tells us what happened. Plus, how online publisher Salon.com plans to use digital currencies to offset revenue lost to ad-blocking software. Salon chief executive Jordan Hoffner talks to us. And why Estonian startup WePower thinks Initial Coin Offerings are the best way to fund cleaner energy. Presented by Rory Cellan-Jones, with BBC tech reporter Perveen Akhtar, and special guest Adriana Hamacher, managing editor of Blockchain News.

(Image: Coins stacked against an abstract circuit board background, Credit: Getty Images).