Path traversal occurs when a file operation escapes its intended location because untrusted input influences the path. A path traversal assessment checks which files the application can actually read or write, how it resolves a requested location, and whether the result stays inside the approved storage area.
A secure login does not settle this question. A signed-in user may be allowed to download one report while the download handler has filesystem access to many unrelated files.
Where should a business look for file path risks?
Inventory report downloads, document previews, archive extraction, theme selection, and import jobs. For each feature, identify whether the client supplies a filename, a relative path, or an opaque document ID that the server resolves itself.
OWASP’s path traversal overview describes how manipulated relative or absolute paths can reach files outside an intended directory. The practical impact also depends on what the application process is permitted to access.
For an illustrative insurance portal, distinguish a policy document’s display name from its storage location. A customer should be able to recognize a document without receiving authority to select arbitrary server files.
What is the difference between path traversal and IDOR?
Path traversal concerns where a file operation resolves. IDOR concerns whether the caller may access the selected business object. A download can need both controls: an authorized document must map to an allowed storage location.
Create separate acceptance rules for the insurance example. The customer may download their own policy, may not download another customer’s policy, and may not select a file outside the document store. Keeping these cases separate helps engineering identify the control each failure needs.
How can the boundary be tested without reading secrets?
Ask the application owner to place a harmless marker file outside the intended test download directory but within the designated test environment. Use another marker inside the allowed directory as the positive control.
Agree which input variations the assessment may exercise and observe the resolved path through application instrumentation when available. The desired result is an allowed download for the intended file and rejection for the out-of-bounds marker.
If a marker outside the directory is returned, retain only the benign evidence needed to show the boundary failure. There is no need to retrieve configuration files, credentials, or real customer material to prove that the path escaped.
Which implementation details deserve review?
Follow the value from request parsing to the final file operation. Note any decoding, normalization, path joining, or filesystem link resolution in between. A check is useful only if it governs the same location the application ultimately opens.
Prefer server-managed mappings from document IDs to known locations where the product allows them. For features that genuinely need paths, use the platform’s established path handling and verify containment with the actual filesystem behavior. A string prefix that happens to resemble the approved directory is not sufficient evidence of containment.
For archives, review the destination of each extracted entry. Reading a download and writing an archive’s contents are separate operations with separate consequences, so document whether both were in scope.
What should a path traversal retest prove?
Repeat the harmless out-of-bounds case, the normal download, and legitimate filenames the business supports, including spaces and international characters where applicable. Confirm that the fix did not make authorized policy documents unavailable.
For a Ceron assessment, supply a test storage area, marker files, and the file workflows to review. The report should identify the input, intended directory, observed operation, process permissions, and verified result after remediation.
File upload processing security covers the earlier stages of document handling. Presigned download URLs covers access carried by a temporary link. The insurance portal is illustrative.
