HTML Code Appears in Description Fields
If you add any HTML code in the description fields, the code appears to be not rendered properly
As per the Restricted Functions in Atlassian Cloud regarding the HTML in issue fields:
This feature creates an XSS vulnerability that could allow malicious users to gain system administrator permissions and use the Cloud infrastructure for nefarious purposes. Wiki markup is still available.
The description field accepts only either wiki markup or text format. Convert the HTML markup to one of them.