Invisible Characters In Solarwinds Node Custom Properties

I’ve had an open issue for the last few weeks regarding why “odd” characters were showing up in Custom Property fields in my company’s Solarwinds Orion/Network Performance Monitor install. I detected them when I put a business-rules-integrity-checker in place, but I didn’t know where they came from. I cleaned up all the existing cases and waited to see if it would happen again. It did, and now I know where they came from and, I think, why.

Even after I understood the problem I couldn’t Google up any references to this situation, so I’m documenting it. One caveat – we’re running a non-current version of NPM (10.1.3; yes, we’re working on upgrading) so the issue I’m going to describe may not exist in later versions.
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