Xss Cross Site Scripting in Axum with Dynamodb

Cross-site scripting (XSS) in an Axum application that stores and retrieves data from DynamoDB typically arises when untrusted data is rendered in an HTML context without proper encoding. DynamoDB itself is a NoSQL database and does not execute or store HTML/JavaScript, so the vulnerability is not in DynamoDB but in how data retrieved from DynamoDB is handled by Axum before being sent to the browser.

Consider an endpoint that fetches a user profile from DynamoDB and injects a user-supplied display name directly into an HTML response:

async fn profile_handler(
    path(name): Path,
    table: Arc, // hypothetical DynamoDB table abstraction
) -> Result {
    let item = table.get_item(&json!({ "username": name })).await?;
    let display_name: String = item.get("displayName").cloned().unwrap_or_default();
    // Unsafe: directly embedding user data into HTML
    let html = format!("
Welcome, {}
", display_name);
    Ok(Html(html))
}

If an attacker registers or updates a profile with displayName set to <script>stealCookies()</script>, the stored value in DynamoDB is benign JSON data. The risk occurs when Axum retrieves the item and embeds it unsanitized into the HTML response, causing the browser to execute the script in the context of your site. This is a reflected or stored XSS pattern enabled by insufficient output encoding, not by DynamoDB behavior.

Another scenario involves unsafe query construction or response serialization in Axum. For example, building a response by concatenating JSON keys into HTML/JS without escaping can lead to injection vectors. Even when using an OpenAPI spec with $ref resolution across definitions, runtime findings from middleBrick’s checks will highlight places where unescaped user-controlled data reaches HTML contexts. middleBrick scans this attack surface and reports XSS findings with severity and remediation guidance, helping you prioritize fixes.

middleBrick’s LLM/AI Security checks are particularly useful when AI-assisted code generation is used to build Axum routes or DynamoDB mappers, as it detects prompt injection attempts and output anomalies that could lead to unsafe data handling patterns. For teams using middleBrick’s Web Dashboard or CLI, XSS findings map to OWASP API Top 10 and provide prioritized remediation steps.

Remediate XSS when working with DynamoDB in Axum by ensuring all data rendered in HTML, JavaScript, or attributes is properly encoded for the target context. Use established HTML-escaping libraries rather than manual string replacement. Below are concrete, working examples for Axum with DynamoDB integration.

1. Safe HTML rendering with proper escaping

Use an HTML-escaping crate such as ammonia or askama::escape. If you use askama for templating, its autoescape feature handles this safely:

<!-- templates/profile.html -->
<!-- askama enables autoescape by default -->
<h1>Welcome, {{ display_name }}</h1>

// handler
async fn profile_handler(
    path(name): Path,
    table: Arc,
    template: Extension<askama::Environment>,
) -> Result<impl IntoResponse> {
    let item = table.get_item(&json!({ "username": name })).await?;
    let display_name: String = item.get("displayName").cloned().unwrap_or_default();
    let ctx = ProfileContext { display_name };
    let body = tpl.render(&ctx)?; // autoescaped output
    Ok(Html(body))
}

2. JSON API responses consumed by a strict frontend

If the frontend is a separate SPA, return JSON and let the client render safely. Ensure the frontend treats any HTML-injection-prone fields as text, not markup. On the server, avoid embedding user data into script blocks:

async fn profile_json_handler(
    path(name): Path<String>,
    table: Arc<DynamoDbTable>,
) -> Result<impl IntoResponse> {
    let item = table.get_item(&json!({ "username": name })).await?;
    // Keep data as plain text; escaping is the frontend’s responsibility
    let display_name: String = item.get("displayName").cloned().unwrap_or_default();
    let body = serde_json::json!({ "displayName": display_name });
    Ok(Json(body))
}

3. Sanitization for limited HTML (if required)

If you must store and render limited HTML (for example, formatted descriptions), use ammonia to sanitize on input or output. Do not rely on DynamoDB to strip scripts:

use ammonia::Builder;

fn sanitize_html(raw: &str) -> String {
    Builder::new()
        .tags(&["b", "i", "em", "strong", "a"])
        .remove_contents_on_any_tag(false)
        .clean(raw)
        .to_string()
}

async fn update_profile(
    body: Json<ProfileUpdate>,
    table: Arc<DynamoDbTable>,
) -> Result<impl IntoResponse> {
    let safe_bio = sanitize_html(&body.bio);
    table.put_item(&json!({ "username": body.username, "bio": safe_bio })).await?;
    Ok(StatusCode::NO_CONTENT)
}

4. Secure data modeling in DynamoDB

Design your DynamoDB items to keep raw user input separate from metadata used in rendering. Store raw strings as attributes, and perform encoding at the application layer. Avoid storing pre-rendered HTML when plain text suffices. middleBrick’s OpenAPI/Swagger analysis can help validate that response schemas do not encourage unsafe embedding patterns.

5. Tooling and scanning

Use middleBrick’s CLI to scan your Axum endpoints and DynamoDB integration for XSS and other findings:

$ middlebrick scan https://api.example.com/openapi.json

For CI/CD, the GitHub Action can fail builds if the security score drops below your chosen threshold, and the MCP Server lets you scan APIs directly from AI coding assistants in your IDE. The Web Dashboard tracks scores over time and provides prioritized remediation guidance.