Have a look at the tutorial about Forena report parameters. In the end, they are technically stored (saved) as part of the so called .frx files (which contains all of your report specification details). Here is a (partial) example of such frx-file:
<title>My Report Title</title>
<frx:parm id="state" label="State" require="1"
desc="Select a state from the list."
data_source="sampledb/states" data_field="" type="select">
So when you're creating ("writing") a report specification (eg using the WYSIWYG report writer), part of what you actually do is saving a special kind of "content" in XHTML format. And that's where the typical "text formats" get involved (just like any kind of content you'd save in Drupal).
However, because of the way Forena does certain things to process these XHTML files (report specifications that Forena massages in reports/charts that match your specifications), it's important that as part of the Forena installation/configuration, you "Prepare a text format to be used by Forena", as explained in the Forena Setup Guide. Here is the crucial part of it:
Regardless as to which Input Format you choose to use with forena, make sure these entries are turned of for the chosen text format :
- Limit allowed HTML tags.
- Display any HTML as plain text.
- Convert line breaks into HTML.
- Correct faulty and chopped off HTML.
Anybody who starts using Forena without completing (or knowing about) this crucial configuration step, will typically run in this first-time configuration error ... Same happened to me when I first tried to use Forena some years ago.