Thanks for looking into this! Unfortunately we do not (yet) have a local server for MapleTA, but this security issue could be an argument for becoming self-hosted. One way around the concrete problem (without self-hosting, I think) is to embed the needed (if not all) *.mla procedures directly via manual copy-paste into the startup code from the worksheet that defines the *.mla file. But this, of course, is much more cumbersome than the wished-for simple one-line reference to the *.mla file itself.
Your answer, however, then also induces a similar question concerning the use of repository files inside MapleTA itself, as thoroughly explained in: [https://mapletacommunity.com/topic/64/how-to-create-and-use-a-maple-repository-in-maple-ta]. Admittedly, I did not check this out yet, but the question is, if this functionality also has been depreciated or blocked in the meantime?
Yes, I'm using the 2016 version. It worked, thank you! I used $x*$response.provachain1.1.1 in the response area, where $x=4; was defined as the only line of the algorithm. Good to know also that it is wrong to consider the (addable by the user) field "id" from "Information Fields" as equivalent to the "id" appearing in the source, which is not the case.