What's the difference between these two phrases?
- their systems’ security posture
- their systems security posture
Is there any difference in the meaning? If not, when we use either of them?
The phrase "[...] their systems' security posture [...]" uses a possessive form to show that security posture quality belongs to the systems.
The phrase "[...] their systems security posture [...]" is using "systems security posture" as a noun phrase, as though "systems security posture" is a thing. This might be a matter of jargon, but I've not heard that expression before. Still, it almost certainly means the exact same thing as the first phrase.
their systems’ security posture
The security posture of their systems.
their systems security posture
The 'systems security' posture of them (whoever 'they' are).