If directory indexing is enabled, document libraries are browsable through the URL not only for site admins but for anyone according to the default Document Library permissions.
This could result in permission / security issues with documents being viewable by incorrect parties.
This article describes how to manage directory indexing in a way that gives you more control across sites.
Directory indexing is disabled in DXP by default because of security reasons as per OWASP, however, enabling it might be needed in certain cases and Liferay offers two ways to do this.
1. The global behavior can be changed with a property which is set to false by default:
We do not recommend to enable this property in most cases because it will be effective for all sites within the portal.
2. "Enable Directory Indexing" toggle for individual site via Site Settings.