Forms for the same-sex marriage survey have only been landing in mailboxes for two days now, but Australians have already exposed potential security flaws with the ballot.
People have reported voting up to seven times after receiving multiple forms at their address thanks to former residents who failed to update their electoral details.
One South Australian man took to Twitter to thank the former residents of his property whose forms he claimed to have used to vote.
"Big ups to the seven people that haven't changed their enrolment info and their vote mail came to my house," he wrote.
"My vote just evolved seven times hahaha."
Others have reported similar scenarios, saying they received multiple voting forms.
"I get SO much mail for previous people who lived in my house. Every damn one of these is being opened and sent back as yes," another person said on Twitter.
Another wrote: "The beauty of this postal survey, receiving three enrolled citizens of previous apartment occupants at your current residential address in your mailbox and using that to your advantage."
A concerning Facebook post highlighted another potential security risk with the ballots.
The image, showing a torch or bright light shone over a sealed ballot envelope could reveal the details of the vote inside and potentially even the unique barcode used to count each response.
The post suggests "any postal worker with a vendetta against the opposing side can go through and remove votes as they see fit".
"Bravo government," the post's author wrote.
News.com.au has contacted the ABS for comment on both these issues.