I am building an uploader, and I want to set a couple of parameters so the client cannot upload any type of file.

This is the cfm file which processes the upload includes/processFileSubmission.cfm:

<cfparam name="form.fileUpload" default="">
<cfparam name="form.hiddenFileInput" default="">
<cfset dirName = expandPath("../../data/images/volvelle/")>

<cfif len(trim(form.fileUpload))>
    <cfset fileName="#form.actual_name#_#form.email#" />
    <cfset fileName=Replace(fileName, " ", "-", "ALL") />
    <cfset fileName=LCase(fileName) />
    <cfset fileSize = createObject("java","java.io.File").init(form.fileUpload)>
    <cfif fileSize.length() LT 52428800>
        <cffile
            action="upload"
            result="upload"
            accept="image/*"
            fileField="fileUpload"
            nameconflict="makeunique"
            destination="#dirName#/#fileName#__#hiddenFileInput#"
        >
    </cfif>
    <cfdump var="#upload#">
    <cfif #upload.CONTENTTYPE# NEQ 'image'>
        <cfoutput>Upload file was not an image</cfoutput> // this does not get reached. 
        <!--- <cflocation url="error.cfm"> --->
    <cfelse>
        <cfoutput>Upload file was an image</cfoutput> // this does get reached for an image file
    </cfif>
</cfif>

In my html I am going to use an accept attribute to filter only for image files, but in order to test this I have currently disabled that (I still need to do a back end check).

So the html was this (index.cfm):

<input class="el-7 button" type="file" name="fileUpload" accept="image/*" />

But is now this:

<input class="el-7 button" type="file" name="fileUpload">

If I upload an image, I can see this output from <cfdump var="#upload#" />

This shows that upload.CONTENTTYPE = image, which is what I am trying to test in my condition at the bottom of the script. I am so-so with cfm but always get mixed up and variable interpolation but I have tried <cfif upload.CONTENTTYPE NEQ 'image'> which did not work either. Not sure if it needs quotes.

However if I then upload a pdf, the cffile fails, but seems to pass back to my confirm.cfm file which should return errors or a success message based on the form inputs.

This is the error:

Accept  image/*
Detail  <br>Only files of type image/* can be uploaded. <br>Verify that you are uploading a file of the appropriate type.
Message The MIME type of the uploaded file application/pdf was not accepted by the server.

This is the content of my confirm.cfm file

<cfparam name="FORM.fileUpload" default="">
<cfparam name="FORM.name" default="">
<cfparam name="FORM.actual_name" default="">
<cfparam name="FORM.email" default="">
<cfparam name="FORM.comments" default="">
<cfparam name="FORM.auth" default="">
<cfparam name="FORM.gcapthca" default="">

<cfif len(trim(form.fileUpload))>
    <cfinclude template="includes/processFileSubmission.cfm">
</cfif>

<cfif len(trim(FORM.auth)) NEQ 0 || len(trim(FORM.name)) NEQ 0>
    <cflocation url="thanks.cfm">
</cfif>

    <div class="content">
    <cfparam name="errors" default="">
        <cfif isDefined ("FORM.submit")>
            <cfif len(trim(FORM.email)) NEQ 0 AND NOT isValid("email", FORM.email)>
                <cfset errors = errors & "<li>Please enter a valid email address</li>">
            </cfif>
            <!--- clean up variables --->
            <cfset FORM.fileUpload="">
            <cfset FORM.name="">
            <cfset FORM.actual_name="">
            <cfset FORM.email="">
            <cfset FORM.comments="">
            <cfset FORM.gcapthca="">
            <cfoutput>
                <form method="post" action="#CGI.SCRIPT_NAME#" class="m-t-5">
                    <input type="hidden" name="submitted" value="true">
                    <cfif LEN(errors) GT 0><!--- checking for errors --->
                    Errors
                    <ul class="errors">
                        #errors#
                    </ul>
                    <a href="javascript:history.back(1)">Go back</a>
                    <cfelse>
                        Thank you. Your file has been submitted.<br />
                        <a href="/">slackwise</a><br />
                        e: email address
                        We never disclose email addresses to third parties.
                    </cfif>
                </form>
            </cfoutput>
        </cfif>
    </div>

All of this code works, it worked for a simple feedback form, I just need some error handling for the image uploader which is new.

TL/DR

I want to have a specific file redirect if the user tries to upload a non-image file. However in addition it might also be useful to have some generic fallback redirect page in case of any other type of error. How do I implement this?