diff --git a/dashcaddy-api/__tests__/public-route-placeholders.test.js b/dashcaddy-api/__tests__/public-route-placeholders.test.js
new file mode 100644
index 0000000..9c23405
--- /dev/null
+++ b/dashcaddy-api/__tests__/public-route-placeholders.test.js
@@ -0,0 +1,89 @@
+/**
+ * Regression tests for PUBLIC_ROUTES / CSRF excludedPaths `:param` placeholder
+ * matching. Pre-DC-053 these were literal-string comparisons, so
+ * `/api/v1/share/:token/preview` never matched real request paths like
+ * `/api/v1/share/abc123/preview`. Fixed by converting `:param` to a
+ * `[^/]+` regex segment before testing. Caught during DC-053 live testing.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+const os = require('os');
+
+function _tmpDir() {
+  return fs.mkdtempSync(path.join(os.tmpdir(), 'dashcaddy-public-test-'));
+}
+function _cleanup(dir) {
+  try { fs.rmSync(dir, { recursive: true, force: true }); } catch {}
+}
+
+const SRC_MIDDLEWARE = path.join(__dirname, '..', 'src', 'utilities', 'middleware.js');
+const SRC_CSRF = path.join(__dirname, '..', 'src', 'security', 'csrf-protection.js');
+
+describe('PUBLIC_ROUTES + CSRF excludedPaths: `:param` placeholder matching', () => {
+  test('PUBLIC_ROUTES is parsed and contains the DC-053 share entries', () => {
+    const content = fs.readFileSync(SRC_MIDDLEWARE, 'utf8');
+    // Sanity: file should still contain the public share entries
+    expect(content).toContain('/api/v1/share/:token/preview');
+    expect(content).toContain('/api/v1/share/:token/subscribe');
+    expect(content).toContain('/api/v1/share/:token/redeem-tailscale');
+  });
+
+  test('CSRF excludedPaths contains the DC-053 share entries', () => {
+    const content = fs.readFileSync(SRC_CSRF, 'utf8');
+    expect(content).toContain('/api/v1/share/:token/subscribe');
+    expect(content).toContain('/api/v1/share/:token/redeem-tailscale');
+  });
+
+  test('PUBLIC_ROUTES contains the DC-048 invite entries (regression coverage)', () => {
+    const content = fs.readFileSync(SRC_MIDDLEWARE, 'utf8');
+    expect(content).toContain('/api/v1/auth/invites/:token');
+    expect(content).toContain('/api/v1/auth/invites/:token/accept');
+  });
+
+  test('CSRF excludedPaths contains the DC-048 invite entry', () => {
+    const content = fs.readFileSync(SRC_CSRF, 'utf8');
+    expect(content).toContain('/api/v1/auth/invites/:token/accept');
+  });
+
+  // Behavioral test: the regex conversion that the middleware applies to a
+  // `:param` entry should match real request paths. This exercises the SAME
+  // algorithm used by `isPublicRoute()` in src/utilities/middleware.js and
+  // `isExcluded` in src/security/csrf-protection.js, just in isolation.
+  function _placeholderToRegex(p) {
+    return '^' + p.replace(/:[A-Za-z_][A-Za-z0-9_]*/g, '[^/]+') + '$';
+  }
+
+  test('placeholder-to-regex algorithm matches share preview paths', () => {
+    const pattern = _placeholderToRegex('/api/v1/share/:token/preview');
+    expect(new RegExp(pattern).test('/api/v1/share/abc123/preview')).toBe(true);
+    expect(new RegExp(pattern).test('/api/v1/share/some-very-long-token/preview')).toBe(true);
+    // Different method/path segments should not match
+    expect(new RegExp(pattern).test('/api/v1/share/abc/extra/preview')).toBe(false);
+    expect(new RegExp(pattern).test('/api/v1/share/preview')).toBe(false);
+  });
+
+  test('placeholder-to-regex matches multi-param paths', () => {
+    const pattern = _placeholderToRegex('/api/v1/auth/login/:provider/verify');
+    expect(new RegExp(pattern).test('/api/v1/auth/login/totp/verify')).toBe(true);
+    expect(new RegExp(pattern).test('/api/v1/auth/login/email/verify')).toBe(true);
+    expect(new RegExp(pattern).test('/api/v1/auth/login/totp/initiate')).toBe(false);
+  });
+
+  test('placeholder-to-regex handles exact paths (no placeholders)', () => {
+    const pattern = _placeholderToRegex('/health/live');
+    expect(new RegExp(pattern).test('/health/live')).toBe(true);
+    expect(new RegExp(pattern).test('/health/ready')).toBe(false);
+  });
+
+  test('placeholder-to-regex handles the auth/gate/ prefix exemption', () => {
+    // /api/v1/auth/gate/ is a prefix match (not in PUBLIC_ROUTES entries
+    // individually). Verify the algorithm preserves this by NOT requiring
+    // placeholders when none are present.
+    const pattern = _placeholderToRegex('/api/v1/auth/gate/foo');
+    expect(new RegExp(pattern).test('/api/v1/auth/gate/foo')).toBe(true);
+    expect(new RegExp(pattern).test('/api/v1/auth/gate/bar')).toBe(false);
+  });
+});
\ No newline at end of file
diff --git a/dashcaddy-api/src/security/csrf-protection.js b/dashcaddy-api/src/security/csrf-protection.js
index 6df9c52..fd92c61 100644
--- a/dashcaddy-api/src/security/csrf-protection.js
+++ b/dashcaddy-api/src/security/csrf-protection.js
@@ -172,8 +172,16 @@ function csrfValidationMiddleware(req, res, next) {
     '/api/v1/system/update-notify'
   ];
 
-  const isExcluded = excludedPaths.some(path => req.path === path) ||
-                     req.path.startsWith('/api/v1/auth/gate/');
+  const isExcluded = excludedPaths.some(path => {
+    if (req.path === path) return true;
+    // Allow `:param` placeholders to match any single segment. Pre-existing
+    // bug — literal ':token' never matched real tokens — fixed under DC-053.
+    if (path.includes(':')) {
+      const pattern = '^' + path.replace(/:[A-Za-z_][A-Za-z0-9_]*/g, '[^/]+') + '$';
+      return new RegExp(pattern).test(req.path);
+    }
+    return false;
+  }) || req.path.startsWith('/api/v1/auth/gate/');
 
   if (isExcluded) {
     return next();
diff --git a/dashcaddy-api/src/utilities/middleware.js b/dashcaddy-api/src/utilities/middleware.js
index 55631ca..e7ec8b8 100644
--- a/dashcaddy-api/src/utilities/middleware.js
+++ b/dashcaddy-api/src/utilities/middleware.js
@@ -392,6 +392,17 @@ module.exports = function configureMiddleware(app, {
   function isPublicRoute(req) {
     return PUBLIC_ROUTES.some(r => {
       if (r.method && req.method !== r.method) return false;
+      if (r.exact) {
+        // Exact string match, BUT allow `:param` placeholders in the
+        // PUBLIC_ROUTES entry to match any single path segment. This was a
+        // pre-existing bug — literal ':token' never matched real tokens —
+        // caught by DC-053 public share preview returning 401.
+        if (r.path.includes(':')) {
+          const pattern = '^' + r.path.replace(/:[A-Za-z_][A-Za-z0-9_]*/g, '[^/]+') + '$';
+          return new RegExp(pattern).test(req.path);
+        }
+        return req.path === r.path;
+      }
       return r.prefix ? req.path.startsWith(r.path) : req.path === r.path;
     });
   }