docs(lint): add protected vars

sidebar/sidebar.ts

@@ -54,6 +54,7 @@ const docs = [
               { text: "erc20-unchecked-transfer", link: "/forge/linting/erc20-unchecked-transfer" },
               { text: "incorrect-exp", link: "/forge/linting/incorrect-exp" },
               { text: "incorrect-shift", link: "/forge/linting/incorrect-shift" },
+              { text: "protected-vars", link: "/forge/linting/protected-vars" },
               { text: "reentrancy-eth", link: "/forge/linting/reentrancy-eth" },
               { text: "rtlo", link: "/forge/linting/rtlo" },
               { text: "unchecked-call", link: "/forge/linting/unchecked-call" },

src/pages/forge/linting.mdx

@@ -163,6 +163,7 @@ navigation on the right to browse by severity.
 - [`erc20-unchecked-transfer`](/forge/linting/erc20-unchecked-transfer) — Flags calls to ERC20 `transfer` and `transferFrom` where the boolean return value is ignored.
 - [`incorrect-exp`](/forge/linting/incorrect-exp) — Flags `^` (bitwise xor) used between integer literals where `**` (exponentiation) was almost certainly intended.
 - [`incorrect-shift`](/forge/linting/incorrect-shift) — Flags shift operations where a literal appears on the left and a non-literal on the right, which is almost always the wrong operand order.
+- [`protected-vars`](/forge/linting/protected-vars) — Flags externally callable functions that can write an annotated state variable without invoking its declared protection.
 - [`reentrancy-eth`](/forge/linting/reentrancy-eth) — Flags uncapped ETH-transferring low-level `call` operations when state read before the call is written after the call.
 - [`rtlo`](/forge/linting/rtlo) — Flags the presence of Unicode bidirectional override characters in source code, which can be used to hide malicious behavior ("Trojan Source", [CVE-2021-42574](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-42574)).
 - [`unchecked-call`](/forge/linting/unchecked-call) — Flags low-level calls (`call`, `delegatecall`, `staticcall`, `callcode`) whose `success` return value is ignored.

src/pages/forge/linting/protected-vars.mdx

@@ -0,0 +1,79 @@
+---
+description: State writes that bypass declared protection
+---
+
+## Protected variables
+
+**Severity**: `High`
+**ID**: `protected-vars`
+
+Flags externally callable functions that can write a state variable without invoking the function
+or modifier named by its `@custom:security write-protection` annotation.
+
+### What it does
+
+A state variable can declare a required protection with an exact function or modifier signature:
+
+```solidity
+/// @custom:security write-protection="onlyOwner()"
+address owner;
+```
+
+The lint follows modifiers, library calls, and resolved internal call paths from public, external,
+fallback, and receive entry points. If an entry point writes the variable directly or through a
+reachable helper, the required function or modifier must also be reachable from that entry point.
+This includes writes through storage references, returned storage locations, collection
+`push`/`pop` operations, and resolvable inline-assembly storage slots.
+
+Overloads are matched by their exact signature. Inherited variables, entry points, functions, and
+modifiers are resolved in the most-derived contract, including virtual dispatch. External calls
+such as `this.onlyOwner()` do not satisfy an internal write-protection requirement. An unresolved
+signature or malformed `write-protection` value is treated as unsatisfied so an invalid annotation
+cannot silently disable the lint.
+
+Like Slither's annotation semantics, this rule is reachability-based rather than order- or
+path-sensitive: the annotation identifies a required internal call, not a proof that the call
+dominates every write.
+
+### Why is this bad?
+
+Writing security-sensitive state without its declared access check can let an untrusted caller
+change ownership, authorization, or other protected configuration.
+
+### Example
+
+#### Bad
+
+```solidity
+contract Registry {
+    /// @custom:security write-protection="onlyOwner()"
+    address public owner;
+
+    modifier onlyOwner() {
+        require(msg.sender == owner);
+        _;
+    }
+
+    function setOwner(address newOwner) external {
+        owner = newOwner;
+    }
+}
+```
+
+#### Good
+
+```solidity
+contract Registry {
+    /// @custom:security write-protection="onlyOwner()"
+    address public owner;
+
+    modifier onlyOwner() {
+        require(msg.sender == owner);
+        _;
+    }
+
+    function setOwner(address newOwner) external onlyOwner {
+        owner = newOwner;
+    }
+}
+```