Windows security warning (ActiveX) when clicking into fields in ArcToolbox tool?

I found a solution that worked for me.

I change setting in the register. Search for 1201 and value 0 (DWORD) at: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\0

Problem running any tool (on Esri's Geonet forums)

The one important difference that most suggestions omit, and very possibly this is all that's needed to fix this, is that in Zone 0 a new DWORD 1201 MUST be created if it doesn't already exist. In other words changing all the other DWORD values to "0" will not work unless 1201 is also added.

The solution can be found here: https://geonet.esri.com/ideas/13563-fix-activex-security-bug-for-toolbox-scripts

Add a "DWORD" entry called "1201" to the "HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Zones\0" folder and set the value to 0. Restart ArcGIS for it to take effect.

I see that a few posts were deleted from here; one that correctly identifies the problem as a recent windows update which it was, the other which states that adding the DWORD solves the problem. Perhaps, leaving correcting these posts to sound more like answer and not deleting them would have been a better approach since the actual accepted answer here is incomplete.

Quick and short solution:

• Please follow this post: REDIRECT: axtiveX error warning

Original Posting

I found a fix for this on ESRI's web site - axtiveX error warning. A staff member came into the thread and confirmed it is a bug in current versions of ArcGIS (at time of writing, 10.5.1 was the latest).

So far we have only seen it affect our 1703 users. Haven't tested on 1709, but I'm going to imagine it also affects them too. At my org we are not allowed to change security zone's as the other answer's states (policy for this setting is controlled far higher up the chain), but the link above has a workaround (or possibly actual fix?). I hear they are supposed to have this in 10.6.

Some of our users reported this issue to Esri Support a few weeks ago. We have reported this issue as a defect to our development teams. They are well aware and are investigating this issue at their end.

"BUG-000105427: ActiveX control warnings appear when interacting with geoprocessing tools after updating to Windows 10 version 1703 (Creators Update)".

They link to their knowledge base article on how to fix it: Bug: Internet Explorer script errors are generated when running any geoprocessing tool from ArcToolbox on some systems that implement folder redirection

Essentially you need to copy their .xsl files into your arctoolbox folder, which for 10.5 (by default) is located at C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcToolbox\Stylesheets. While the link to this page shows an error that looks very different from the one you describe it seems to be the same issue, just an old version of internet explorer. I confirmed it was working for a few of our users.