Nicholas Hawkes, 39, from Basildon, admitted targeting a woman and a teenage girl with the indecent images showing an exposed penis.
Appearing in the dock at Southend magistrates court, he pleaded guilty to two incidents of cyber flashing on Friday, February 9.
He was remanded in custody by District Judge Christopher Williams, to be sentenced at Basildon crown court next month.
The conviction comes less than two weeks after the Crown Prosecution Service introduced new powers to prosecute crimes including cyber flashing, sharing nude ‘deepfake’ images, and the practice of ‘down-blousing’.
Hawkes used WhatsApp to send the naked images of male genitalia to his victims, and the CPS said the offence is often carried out via social media or using Bluetooth or Airdrop links to phones.
The Online Safety Act was passed into law in October last year, making it a criminal offence punishable by up to two years in prison for sending unsolicited images of genitals.
Prosecutors can judge whether to bring cases based on the impact on the victim, if they are alarmed, distressed, or humiliated, and if the person sending the image hoped to gain sexual gratification.
Siobhan Blake, from the CPS, said: “Women and girls should be able to go about their lives and daily commutes without being subjected to and bombarded with unwanted sexual images. Our prosecutors are ready and committed to tackling this unacceptable behaviour.
“We would encourage anyone who has been subjected to the illegal act of cyberflashing to come forward and report it. This is a serious crime, and we will work with police to build strong cases against offenders who use technology to harass, distress and abuse victims for their own pleasure.
“The Online Safety Act and our accompanying guidance will give prosecutors powerful tools needed to go further in safeguarding women and girls against predatory online behaviours. These will also allow us to send before the courts and bring to justice those who hide behind computer screens and smartphones to carry out their abusive behaviours.”
The court heard Hawkes has previous convictions for sexual offences, including two incidents last year when he stripped naked in public.
He is already a registered sex offender, and will be sentenced for breaching a suspended sentence order together with the two offences of cyber flashing.
Sentencing has been set for the week of March 11.