Rewrite 548 skill descriptions to the activation rubric

Each rewritten description now states both what the skill does (concrete
capability, named tools/artifacts) and an explicit when-to-use trigger,
improving agent discovery/activation. Grounded in each skill's own body;
changes confined to the `description` field only (bodies and all other
frontmatter untouched). Produced by a gated audit->rewrite->recheck loop
(548 -> 0 flagged) with a sampled anti-invention check (0 ungrounded).

Schema: 817/817 pass. Framework-ID gate: 0 defects.

skills/exploiting-mass-assignment-in-rest-apis/SKILL.md

@@ -1,8 +1,12 @@
 ---
 name: exploiting-mass-assignment-in-rest-apis
-description: Discover and exploit mass assignment vulnerabilities in REST APIs to
-  escalate privileges, modify restricted fields, and bypass authorization controls
-  by injecting unexpected parameters in API requests.
+description: >-
+  Discovers and exploits mass assignment (autobinding) in REST APIs by injecting
+  unexpected or hidden parameters (e.g. role, isAdmin, plan) into create/update
+  requests, using Burp Suite Intruder, Arjun, and param-miner to find bindable
+  fields on ORM-backed endpoints (Rails, Django, Laravel, Spring). Use when testing
+  REST APIs for privilege escalation or authorization bypass via unintended
+  parameter binding.
 domain: cybersecurity
 subdomain: web-application-security
 tags: