Auto Action set a cb field content

Forgive what is probably a simple question but how do I set a field value within the action tab for a code type Auto Action?

Something like ...

[cb_profile_title] = $_GET["param1"];

Ensure you've a Field auto action type selected. Then under Action the below should work fine.

Field: cb_profile_title
Operator: Set
Value: [get_param1]

Note you should apply filtering when grabbing raw values like that though. The below for example would filter the value to a string.

Action
Field: cb_profile_title
Operator: Set
Value: [cb:parse function="clean" method="string"][get_param1][/cb:parse]
Parameters
Format Functions: Yes

Ok so I've switched to a Field Auto Action.

The action is manually triggered using the below URL.

index.php?option=com_comprofiler&view=pluginclass&plugin=cbautoactions&action=action&actions=97&Itemid=181&fav=350

Plan was to pick up that "fav" query string value and set the field. So following your advice (simple first, input validated after) I've set...

Field: cb_profile_title
Operator: Set
Value: [get_fav]

However when I trigger the action the cb_profile_title becomes "[get_fav]" rather than "350".

I'm also echoing out under the out tab and [get_fav] is showing 350 on the output. I must be missing something??

Substitutions is on.

Nope never mind. It's suddenly started working.

What trigger are you using? It shouldn't have any issues grabbing GET values. Please be sure you add filtering to it. You're storing raw user input, which is dangerous. Since it's an integer you can use the below to be sure it's filter to integer at all times.

Action
Field: cb_profile_title
Operator: Set
Value: [cb:parse function="clean" method="int"][get_fav][/cb:parse]
Parameters
Format Functions: Yes

I'm triggering the action directly when user clicks on a link. I'm not handling any of the predefined events.