The flaws have been discovered in apps like Snapchat and Facebook Poke, used by many for sexting because they automatically delete images after one to 10 seconds and notify users if recipients take screen shots.
However, experts say "safe sexting" is impossible.
Other security flaws in the apps include the ability for receivers to upload photos onto their computer before opening them. Snapchat itself has also been found to expose a user's email address without their knowledge in the past.
The latest glitch was revealed by a hacker who demonstrated Snapchat screenshots could be taken without notifying the sender.
The commander of the Sex Crimes Squad, Detective Superintendent John Kerlatec, said that teens and adults should think twice about sending a sexually explicit message.
"Once that image appears on a screen, a screen shot can be taken and distributed anywhere, and can last forever," the Sydney morning Herald quoted him as saying.
Detective Kerlatec said people who used the apps could face criminal charges.
Director of Cybersafe Solutions, Susan McLean, also warned against the use of "safe sexting" apps. She said she believed it was only a matter of time before security flaws showed up.
The apps lulled people into "a false sense of security" with publicity saying the images will disappear.