The AFL's official website suffered an embarrassing security lapse today after the home page was defaced with a comment about league chief executive Andrew Demetriou and Collingwood president Eddie McGuire.

Website readers raced to social media to discuss and expose the lapse after the afl.com.au content management system "inadvertently" briefly allowed anyone administrator access.

Journalist Megan Clement tweeted this image after she noticed the AFL site was giving all users admin access. Photo: Megan Clement/Supplied

Megan Clement, a journalist with theconversation.edu.au, tweeted an image at 1:26pm with the site showing the following message: "Demetriou is Eddie's bitch". Another claimed she saw the comment "Magpies suck" on the Collingwood Football Club page.

AFL corporate affairs spokesman James Tonkin confirmed the incident and said the league was working with Telstra to investigate the breach.