Update Privilege Escalation's Weak SessionID Section

[ThunderSon]

What's the issue?
Privilege Escalation guide contains a section at the end called Weak SessionID that feels a bit out of place and could take a rewrite

How do we solve it?
See if the section is still required, if it can be merged into other sections, or if it simply needs a better rewrite to belong to the rest of the content

Would you like to be assigned to this issue?
Check the box if you will submit a PR to fix this issue. Please read CONTRIBUTING.md.

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