diff --git a/backend/src/activitypub/actors/index.ts b/backend/src/activitypub/actors/index.ts
index e88e11d..671f6f3 100644
--- a/backend/src/activitypub/actors/index.ts
+++ b/backend/src/activitypub/actors/index.ts
@@ -43,32 +43,41 @@ export async function get(url: string | URL): Promise<Actor> {
 
 	const data = await res.json<any>()
 	const actor: Actor = { ...data }
-	actor.id = new URL(data.id)
+	actor.id = new URL(actor.id)
 
-	if (data.content) {
-		actor.content = await sanitizeContent(data.content)
+	if (actor.summary) {
+		actor.summary = await sanitizeContent(actor.summary)
+		if (actor.summary.length > 500) {
+			actor.summary = actor.summary.substring(0, 500)
+		}
 	}
-	if (data.name) {
-		actor.name = await getTextContent(data.name)
+	if (actor.name) {
+		actor.name = await getTextContent(actor.name)
+		if (actor.name.length > 30) {
+			actor.name = actor.name.substring(0, 30)
+		}
 	}
-	if (data.preferredUsername) {
-		actor.preferredUsername = await getTextContent(data.preferredUsername)
+	if (actor.preferredUsername) {
+		actor.preferredUsername = await getTextContent(actor.preferredUsername)
+		if (actor.preferredUsername.length > 30) {
+			actor.preferredUsername = actor.preferredUsername.substring(0, 30)
+		}
 	}
 
 	// This is mostly for testing where for convenience not all values
 	// are provided.
 	// TODO: eventually clean that to better match production.
-	if (data.inbox !== undefined) {
-		actor.inbox = new URL(data.inbox)
+	if (actor.inbox !== undefined) {
+		actor.inbox = new URL(actor.inbox)
 	}
-	if (data.following !== undefined) {
-		actor.following = new URL(data.following)
+	if (actor.following !== undefined) {
+		actor.following = new URL(actor.following)
 	}
-	if (data.followers !== undefined) {
-		actor.followers = new URL(data.followers)
+	if (actor.followers !== undefined) {
+		actor.followers = new URL(actor.followers)
 	}
-	if (data.outbox !== undefined) {
-		actor.outbox = new URL(data.outbox)
+	if (actor.outbox !== undefined) {
+		actor.outbox = new URL(actor.outbox)
 	}
 
 	return actor
diff --git a/backend/src/errors/index.ts b/backend/src/errors/index.ts
index c1f552b..63b22cf 100644
--- a/backend/src/errors/index.ts
+++ b/backend/src/errors/index.ts
@@ -7,7 +7,7 @@ type ErrorResponse = {
 
 const headers = {
 	...cors(),
-	'content-type': 'application/json',
+	'content-type': 'application/json; charset=utf-8',
 } as const
 
 function generateErrorResponse(error: string, status: number, errorDescription?: string): Response {
@@ -57,3 +57,7 @@ export function exceededLimit(detail: string): Response {
 export function resourceNotFound(name: string, id: string): Response {
 	return generateErrorResponse('Resource not found', 404, `${name} "${id}" not found`)
 }
+
+export function validationError(detail: string): Response {
+	return generateErrorResponse('Validation failed', 422, detail)
+}
diff --git a/backend/test/activitypub.spec.ts b/backend/test/activitypub.spec.ts
index 6a46173..9162a86 100644
--- a/backend/test/activitypub.spec.ts
+++ b/backend/test/activitypub.spec.ts
@@ -22,43 +22,89 @@ const vapidKeys = {} as JWK
 const domain = 'cloudflare.com'
 
 describe('ActivityPub', () => {
-	test('fetch non-existant user by id', async () => {
-		const db = await makeDB()
+	describe('Actors', () => {
+		test('fetch non-existant user by id', async () => {
+			const db = await makeDB()
 
-		const res = await ap_users.handleRequest(domain, db, 'nonexisting')
-		assert.equal(res.status, 404)
-	})
+			const res = await ap_users.handleRequest(domain, db, 'nonexisting')
+			assert.equal(res.status, 404)
+		})
 
-	test('fetch user by id', async () => {
-		const db = await makeDB()
-		const properties = {
-			summary: 'test summary',
-			inbox: 'https://example.com/inbox',
-			outbox: 'https://example.com/outbox',
-			following: 'https://example.com/following',
-			followers: 'https://example.com/followers',
-		}
-		const pubKey =
-			'-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----'
-		await db
-			.prepare('INSERT INTO actors (id, email, type, properties, pubkey) VALUES (?, ?, ?, ?, ?)')
-			.bind(`https://${domain}/ap/users/sven`, 'sven@cloudflare.com', 'Person', JSON.stringify(properties), pubKey)
-			.run()
+		test('fetch user by id', async () => {
+			const db = await makeDB()
+			const properties = {
+				summary: 'test summary',
+				inbox: 'https://example.com/inbox',
+				outbox: 'https://example.com/outbox',
+				following: 'https://example.com/following',
+				followers: 'https://example.com/followers',
+			}
+			const pubKey =
+				'-----BEGIN PUBLIC KEY-----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-----END PUBLIC KEY-----'
+			await db
+				.prepare('INSERT INTO actors (id, email, type, properties, pubkey) VALUES (?, ?, ?, ?, ?)')
+				.bind(`https://${domain}/ap/users/sven`, 'sven@cloudflare.com', 'Person', JSON.stringify(properties), pubKey)
+				.run()
 
-		const res = await ap_users.handleRequest(domain, db, 'sven')
-		assert.equal(res.status, 200)
+			const res = await ap_users.handleRequest(domain, db, 'sven')
+			assert.equal(res.status, 200)
 
-		const data = await res.json<any>()
-		assert.equal(data.summary, 'test summary')
-		assert(data.discoverable)
-		assert(data['@context'])
-		assert(isUrlValid(data.id))
-		assert(isUrlValid(data.url))
-		assert(isUrlValid(data.inbox))
-		assert(isUrlValid(data.outbox))
-		assert(isUrlValid(data.following))
-		assert(isUrlValid(data.followers))
-		assert.equal(data.publicKey.publicKeyPem, pubKey)
+			const data = await res.json<any>()
+			assert.equal(data.summary, 'test summary')
+			assert(data.discoverable)
+			assert(data['@context'])
+			assert(isUrlValid(data.id))
+			assert(isUrlValid(data.url))
+			assert(isUrlValid(data.inbox))
+			assert(isUrlValid(data.outbox))
+			assert(isUrlValid(data.following))
+			assert(isUrlValid(data.followers))
+			assert.equal(data.publicKey.publicKeyPem, pubKey)
+		})
+
+		test('sanitize Actor properties', async () => {
+			globalThis.fetch = async (input: RequestInfo) => {
+				if (input === 'https://example.com/actor') {
+					return new Response(
+						JSON.stringify({
+							id: 'https://example.com/actor',
+							type: 'Person',
+							summary: "it's me, Mario. <script>alert(1)</script>",
+							name: 'hi<br />hey',
+							preferredUsername: 'sven <script>alert(1)</script>',
+						})
+					)
+				}
+				throw new Error(`unexpected request to "${input}"`)
+			}
+
+			const actor = await actors.get('https://example.com/actor')
+			assert.equal(actor.summary, "it's me, Mario. <p>alert(1)</p>")
+			assert.equal(actor.name, 'hi hey')
+			assert.equal(actor.preferredUsername, 'sven alert(1)')
+		})
+
+		test('Actor properties limits', async () => {
+			globalThis.fetch = async (input: RequestInfo) => {
+				if (input === 'https://example.com/actor') {
+					return new Response(
+						JSON.stringify({
+							id: 'https://example.com/actor',
+							type: 'Person',
+							summary: 'a'.repeat(612),
+							name: 'b'.repeat(50),
+							preferredUsername: 'c'.repeat(50),
+						})
+					)
+				}
+				throw new Error(`unexpected request to "${input}"`)
+			}
+
+			const actor = await actors.get('https://example.com/actor')
+			assert.equal(actor.summary, 'a'.repeat(500))
+			assert.equal(actor.name, 'b'.repeat(30))
+			assert.equal(actor.preferredUsername, 'c'.repeat(30))
+		})
 	})
 
 	describe('Outbox', () => {
diff --git a/backend/test/mastodon/statuses.spec.ts b/backend/test/mastodon/statuses.spec.ts
index 9025200..41f64a2 100644
--- a/backend/test/mastodon/statuses.spec.ts
+++ b/backend/test/mastodon/statuses.spec.ts
@@ -1010,5 +1010,25 @@ describe('Mastodon APIs', () => {
 			assert.equal(results![0].object_id, note.id.toString())
 			assert.equal(results![1].object_id, note.id.toString())
 		})
+
+		test('reject statuses exceeding limits', async () => {
+			const db = await makeDB()
+			const queue = makeQueue()
+			const actor = await createPerson(domain, db, userKEK, 'sven@cloudflare.com')
+
+			const body = {
+				status: 'a'.repeat(501),
+				visibility: 'public',
+			}
+			const req = new Request('https://example.com', {
+				method: 'POST',
+				headers: { 'content-type': 'application/json' },
+				body: JSON.stringify(body),
+			})
+
+			const res = await statuses.handleRequest(req, db, actor, userKEK, queue, cache)
+			assert.equal(res.status, 422)
+			assertJSON(res)
+		})
 	})
 })
diff --git a/functions/api/v1/statuses.ts b/functions/api/v1/statuses.ts
index e1912b4..8a31595 100644
--- a/functions/api/v1/statuses.ts
+++ b/functions/api/v1/statuses.ts
@@ -74,6 +74,10 @@ export async function handleRequest(
 		return new Response('', { status: 400 })
 	}
 
+	if (body.status.length > 500) {
+		return errors.validationError('text character limit of 500 exceeded')
+	}
+
 	const mediaAttachments: Array<Document> = []
 	if (body.media_ids && body.media_ids.length > 0) {
 		if (body.media_ids.length > 4) {