File permissions control who can read, write, or execute files on the server. On shared hosting, overly broad permissions can turn a small bug into a bigger compromise.
Avoid using 777 permissions as a quick fix. It may make an upload or cache folder work, but it also grants write access far more widely than most sites need.
A common baseline is 644 for normal files and 755 for folders, though your host may have specific requirements. Configuration files should be as restrictive as the application allows.
If a plugin or script asks for broad write permissions, understand why before applying them. Temporary troubleshooting changes should be reverted after the issue is fixed.
Review permissions after migrations, backup restores, and manual uploads because these operations can accidentally change ownership or access levels.