An SEO analyzer is, structurally, a crawler plus a set of third-party integrations you hand credentials to. Most of the security exposure in this category comes from the integrations, not the crawling. Here is what to check before you connect anything.
Most tools request https://www.googleapis.com/auth/webmasters.readonly, which is correct and sufficient — it exposes performance data, index coverage and sitemap status. If a tool asks for auth/webmasters without .readonly, it can submit and delete sitemaps on your property. Some suites also request Google Analytics and Google Ads scopes in the same consent screen. Grant them separately if the tool allows it, and audit what you have granted at your Google Account's third-party access page every few months. Revoking is instant and the tool will simply prompt again.
The classic leak is pointing a cloud-based crawler at staging.example.com, which is protected only by obscurity. The crawler fetches it, the URLs land in the vendor's index, and now your unreleased pages exist in someone else's database. Protect staging with HTTP basic auth and use a desktop crawler that supports credentials — Screaming Frog handles basic auth and form-based login locally, so nothing transits a vendor. If you must use a hosted tool, put staging behind an IP allowlist and add only the vendor's documented crawler ranges.
Rank tracking and backlink APIs issue long-lived keys. Three habits prevent the common accidents: keep keys in environment variables rather than in a saved crawl configuration file, generate a separate key per project so revocation is cheap, and check exported configuration files before sharing them — Screaming Frog's .seospiderconfig and similar files can embed credentials.
A default crawler configuration will happily send 20 concurrent requests to an origin that has never seen more than three. On a shared host or a PHP app with a small worker pool, that is a self-inflicted outage. Set concurrency to 2-5 and add a delay for anything on shared hosting. Respect your own robots.txt during audits, then do a second pass ignoring it if you specifically need to see blocked areas — knowing which findings came from which pass matters.
SEO toolbars typically request permission to read and change data on all sites you visit. That is a genuine capability: an extension with that scope can read pages inside your admin panel, your email client and your bank. Restrict the extension to specific sites where the browser allows it, or enable it on click only. Treat an SEO extension with the same suspicion as any other extension that requests full host permissions.