Any Security Risks of Using Field Merges in URLs?

Hi, we'd like to ask the following questions regarding using field merges in URLs.

[Background]
For some type of our emails, we've started to use a field merge in URLs displayed to users on email.
For a pilot campaign that sent an email to audience of a specific company, we've detected the open rates and click-to-open rates are both almost 100%, implying that security system of the audience's company did bot activities on the emails. This is the first email to use field merge inside, so this might happen when it happens, but I'm not sure what side effects this may have in the future.