The UK Independent Inquiry into Child Sexual Abuse (IICSA) has breached the anonymity of an alleged sexual offences victim by publishing their name on its website.
The person's name appeared online in the title of a document, although it was redacted in the body of the text.
Since the start of the inquiry in March 2015, there have been seven instances of third parties or the person concerned contacting the IICSA to notify it of a data breach.
This is the fourth time the probe has contacted the Information Commissioner's Office (ICO) in relation to potential issues.
The person in question - who has automatic anonymity under the law as someone who has made a complaint of being sexually assaulted - was applying to the IICSA for core participant status.
There are 200 complainant core participants in the inquiry whose identity is protected by its Restriction Order, which aims to preserve the confidentiality of what they say.
Today, a spokesman for the IICSA said: "In terms of the issue yesterday afternoon, we put up a notice of determination document whose title contained the name of an individual - the document itself had the name redacted.
"It was removed as soon as it was brought to our attention and the individual is being contacted and will be offered support. We understand that the document was viewed five times during that period.
"We are reviewing our systems and practices and will be seeking advice to make sure we protect personal data as robustly as possible."
An ICO spokesman said: "We are aware of an incident involving the Independent Inquiry into Child Sexual Abuse and a person's name being published online, and will be making inquiries."