A number of users have reported receiving malware warnings from Avast when accessing the Archive of Our Own. We haven't been hacked, and there is no cause for concern - the warning was a false positive.
Avast is erroneously flagging a file used by New Relic, which we use to monitor our servers (you can see more details in (this thread). New Relic are working with Avast to resolve the issue, and we expect things to be back to normal very shortly (we have had only a small number of reports today).
Thank you to everyone who alerted us to this! If you see something unexpected on the site, we always appreciate hearing about it right away. You can keep track of the latest site status via our Twitter AO3_Status, and contact our Support team via the Support form.