We are uploading html_content via the create/update endpoints for campaigns
POST /emails and PUT /emails/activities/{campaign_activity_id}
We have links within our html that use custom fields as params.
ex.
<a href="https://mywebsite.com?custom_param=[[custom.custom_attr]]">Cool Link</a>
Our problem is the brackets in anchor tags are being url encoded.
ex.
`<a href="https://mywebsite.com?custom_param=%5B%5Bcustom.custom_attr%5D%5D">Cool Link</a>`
So, when the email is sent the value isn't replaced.