Please consider data safety first and do not enable public access with a token to highly sensitive data. Access tokens can be seen by any user accessing the public page and can be used to embed the report also in other pages. Public users can also use drill into the details of the reports and see more data in the same flex.bi account.
Generate URL with public token
If you would like to share a report (or a dashboard) then select Embed report or Embed dashboard from the top right toolbar:
Then select Enable public access with a token . An additional parameter
embed_token is added to the iframe URL . This token is unique for this report (or dashboard) and will be used to authenticate that anonymous users can see report results for this specific report. Note the report data won't be visible to users without this public access token.
If you need to disable sharing of this report then unselect checkbox "Enable public access with token"  and save it. Or you can also regenerate the access token to invalidate the previous one . In both cases, no one will see the data in the published report.
Options for reports and dashboards embedded in iframe
You can change the options of how the report or dashboard will be displayed in the iframe :
with or without header and borders (only for reports)
disable all or enable only some actions that can or cannot be performed by end users in the embedded report or dashboard (expand/drill into, drill through issues, drill across issues, change page selection)
enable results export
enable the automatic refresh option: it could be used, for example, if a report or dashboard is displayed on a large screen in a hallway and should be automatically refreshed to show the latest report results.
Please save the changes before embedding an iframe on another page .
Disable possibility to share reports or dashboards with public token
You can completely disable this feature in the whole flex.bi instance by adding these lines to advanced settings.
[general] embed_reports_with_token = false