Tags disappear from Rich Text Editor source mode
Valid from Pega Version 8.5
When you use Rich Text Editor in HTML source mode, some tags disappear from the markup, which causes backward compatibility issues and data loss.
Cause
Pega Platform™ version 8.5.5 introduced the DOM Purifier security plugin. The plugin removes potentially vulnerable tags, including custom tags, from the raw HTML code in the Rich Text Editor source mode.
Workaround
You can disable the DOM Purifier plugin by adding the the window.disableDomPurifier = true markup to the userWorkForm HTML fragment rule.
Alternatively, as of Pega Platform version 8.5.6, you can add a tag to the allow list by including the window.rteCustomAllowedTags = ['myCustomTag'] snippet in the userWorkForm HTML fragment rule.
In Pega Platform versions 8.5.6 to 8.6, the iframe tag is added to the allow list by default.