Recent changes to the landscape mean that the number of false-negatives will increase, particularly due to: To ensure an address is deliverable, the only way to check this is to send the user an email and have the user take action to confirm receipt.
Beyond confirming that the email address is valid and deliverable, this also provides a positive acknowledgement that the user has access to the mailbox and is likely to be authorized to use it.
Some characters are legal for FAT or NTFS files but illegal for files in Sharepoint documentlibraries.
Using the regular upload UI for Sharepoint you'll encounter a rather unpleasant validation error when uploading a file with funky characters.
Free-form text, especially with Unicode characters, is perceived as difficult to validate due to a relatively large space of characters that need to be whitelisted.Input validation is performed to ensure only properly formed data is entering the workflow in an information system, preventing malformed data from persisting in the database and triggering malfunction of various downstream components.Input validation should happen as early as possible in the data flow, preferably as soon as the data is received from the external party.It's also free-form text input that highlights the importance of proper context-aware output encoding and quite clearly demonstrates that input validation is not the primary safeguards against Cross-Site Scripting — if your users want to type apostrophe (') or less-than sign ( References: Input validation of free-form Unicode text in Python Developing regular expressions can be complicated, and is well beyond the scope of this cheat sheet.There are lots of resources on the internet about how to write regular expressions, including: and the OWASP Validation Regex Repository.